PDF version (495 KB)
Math on the Web: A Status Report
September, 2002
Focus: The Second International MathML Conference
by Robert Miner and Paul Topping, Design Science, Inc.
MathML [1] users, vendors, and supporters gathered at the
Second International
MathML Conference [2] in Chicago on June 2830 to hear presentations on the
expanding world of MathML technology. The mood was decidedly upbeat, driven by
the recent advances in MathML support within web browsers. In particular, the
availability of Design Science's MathPlayer extension for Internet Explorer,
Netscape 7 (based on Mozilla) with builtin MathML support, and David Carlisle's
Universal MathML Style Sheet (UMSS) signaled to the conference attendees that
the "MathML browser problem" was now solved and that it is time to turn our
attention back to the original motivation behind MathML: its ability to serve as
an interchange medium for mathematics. Since MathML equations embedded in
a web page carry mathematical meaning and structure, in theory they allow the readers of such pages to work with them
as
math, rather than just look at them. In this edition of the Status Report, we will
focus on the Second International MathML Conference, while also examining the
proposition that the HTML+MathML Platform allows STM (Science, Technical, and
Medical) publishers, both organizations and
individuals, to add value to their publications over media like
Adobe's PDF [3]. This added value comes in the
form of math that is not only pretty to look at, but with which the reader can
also calculate, graph, analyze, search, and copy into new documents. The HTML+MathML Platform
In past editions of this Report [4], we
have been calling the collection of W3C [5] Recommendations which, in combination,
enable math in web pages, "The HTML Platform". In this Report, we'll (hopefully)
make this concept a bit clearer by renaming it to the "The HTML+MathML
Platform". The main technologies comprising the platform are XML, HTML (or
XHTML), and MathML for encoding content, XSL and CSS for styling and processing
documents, and JavaScript and DOM for scripting of dynamic features in a page.
It is our belief that the HTML+MathML Platform is now fully supported in
popular, modern web browsers and is wellpositioned to become the dominant
medium for online delivery of technical content, for both traditional, static
research papers and dynamic interactive presentations.
Browser Support for MathML
Although past issues of this paper have reported extensively on browser
support for MathML display, we will cover it briefly here for the sake of new
readers and to firmly establish that MathML support in browsers is here and
ready for primetime.
Microsoft Internet Explorer and MathPlayer
MathPlayer [6] is Design Science's MathML Display Engine for
Microsoft's Internet
Explorer (IE) [7] web browser. It currently requires IE 5.5 for Windows or later. Design Science is
committed to making MathPlayer available freeofcharge as a service to the
community. As of this writing, MathPlayer is in the final stages of a public
beta program and is available for free download. The final release of MathPlayer
1.0 is expected to be available by the time you read this.
While MathPlayer is an Internet Explorer "plugin" in the sense that it is
additional software that must be installed that Internet Explorer invokes to
perform a task that it cannot do by itself, MathPlayer is not a "Netscape
plugin". MathPlayer uses technology that has none of the limitations (inability
to resize, align to the baseline of surrounding text, access the rest of the
document, etc.) of the plugin technology introduced in the original Netscape
browser (and still supported by Internet Explorer). Instead, MathPlayer
implements each equation as an object that Internet Explorer treats much like
the other kinds of object (e.g., images, paragraphs, etc.) it directly supports.
Although Internet Explorer is available for platforms other than Windows,
Microsoft has not implemented the key technology, "Behaviors", that makes
MathPlayer possible on those platforms. Design Science is committed to providing
MathPlayer for those platforms when Microsoft makes Behaviors available in those
versions of Internet Explorer. Until that time, the Mozilla and Netscape
browsers will be the browsers of choice for the scientific, technical, and
education communities using platforms other than Windows.
One of MathPlayer's key features is a rightclick menu that allows users to
copy an equation's MathML into any software application that accepts MathML via
the clipboard (draganddrop is also supported). This enables a user to copy
mathematics from the web page into programs like Mathematica, Maple and Mathcad for
calculation, graphing, and further analysis. Math can also be copied into
authoring packages like Design Science's WebEQ Editor
[8] or any HTML or XML editor.
Design Science has plans to expand this menu in future versions of MathPlayer to
include commands that work with other MathMLenabled applications directly
— an "Open With Mathematica" or "Graph with
Maple" command, for example.
Mozilla and Netscape 7
Mozilla [9] is an opensource project derived from the complete rewrite of the Netscape
4 web browser, which Netscape made public in 1998. The Mozilla approach to providing MathML support has been to build
it directly into the browser. MathML support is now enabled in Mozilla 1.0 which
was released in April, 2002. It is available for the Windows, Macintosh (Classic
and OS X), and Linux operating systems.
MathML is also supported in
Netscape 7.0 Preview Release 1 (PR1)
[10] which is
based on Mozilla code. The inclusion of MathML support in this browser is an
important milestone for the MathML community. We thank Netscape for having the
vision to properly support the science, engineering, and education communities.
Together with Internet Explorer/MathPlayer, we believe that Netscape 7's MathML
support finally succeeds in resolving the problem of MathML support in web
browsers.
The Universal MathML Style Sheet (UMSS)
Given the advances in rendering software and coding standards, only one
obstacle to ubiquitous and effective math support remains: different rendering
technologies require bits of "glue code" to signal the browser how to handle the
MathML equations it might encounter in a document. In some cases, this extra
code takes the form of special declarations in the document header. In others,
special wrapper code is required around each equation. In still other cases, a
little code is required in both places. On the surface, this would seem to make
it impossible for an author to publish a single document that simultaneously
works in all rendering environments.
The solution envisioned in the HTML+MathML Platform is a standardized way of
transforming parts of a document on the fly according to rules in a stylesheet.
This powerful new stylesheet language is called
Extensible Stylesheet Language
(XSL) [11], which became a W3C Recommendation in October 2001. XSL rules can take into
account what browser is being used to view the page and what addon rendering
components are installed. This enables authors to ignore the "glue code" that
used to be necessary to fire up a specific rendering component to handle math
notation. Instead, authors generate documents which are strictly
standardscompliant, and at run time, the stylesheet running in the reader's
browser adds whatever glue code is necessary to render MathML based on what is
installed on the reader's system.
Internet Explorer 6 and Netscape 6/7 are the first browsers to fully
implement XSL, the last major piece of the HTML+MathML Platform. To capitalize
on the new technology, the W3C Math Working Group has recently released a
"Universal Math" XSL stylesheet (UMSS)
[12], developed by David Carlisle of LaTeX
fame and an editor of the MathML 2.0 Specification. The stylesheet currently
works with IE6 and Netscape 6.2 and 7.0 PR1, and produces legible renderings of
strictly standardscompliant web documents on a wide variety of platforms.
The Universal Math Style Sheet searches through a list of possible rendering
configurations and uses the first one that matches the reader's system. Authors
can customize the order of the search, to specify a preferred rendering
configuration on systems that have more than one available. In general, the
stylesheet attempts to use native implementations and addon renderers first. If
that fails, it will generate HTML/CSS/JavaScript code on the fly to approximate
traditional math layout in 6.x browsers.
The math rendered by the stylesheet ranges from crude but legible to very
high quality depending on the combination of browser, operating system and
addon software. But for the first time, with the Universal Math stylesheet an
author can be relatively certain that most of his or her readers will actually
be able to see MathML equations in a web page.
MathML Adds Value to STM Publishing
STM (Science, Technical, and Medical) publishers and content providers
currently publish documents containing math using Adobe's PDF (Portable Document
Format) or, sometimes, as HTML with GIF images for the equations. Many of them
are aware of MathML but have adopted a waitandsee attitude due to the long
delay between MathML's initial conception and its recent arrival within the web
browser. Now that browsers can display MathML, it is time for publishers to
reexamine the benefits of publishing in HTML with math expressed in MathML.
Today's publishers are competing with each other on many levels. One of the
most important is that of adding value to their publications. Many publishers
find their content overlaps with that of other publishers and are looking for
ways in which they can add value to their products that will cause readers to
favor their products over those of their competitors. The interactive nature of
the web greatly increases the scope for such valueadding when compared to the
traditional paper medium. We believe that MathML represents a significant
opportunity for STM publishers to add value to their content.
What are the Benefits of MathML?
Please note that most of the benefits listed here are valid for a wide
audience, from the largest
publishing house down to the individual researcher putting research on their
own web site.
 Since MathML encodes more mathematical structure than PDF files or GIFs,
MathML can be used for computation. Major computer algebra systems, such as
Mathematica, Maple, Mathcad, now support cutandpaste of MathML into their
documents enabling their users to transfer math from web pages and other
sources into their documents for further calculation, graphing, searching, and
analysis. These vendors have also deployed MathMLaware
web services for dynamic math on the web applications.
 MathML is a public standard, so there are a variety of interoperable tools and
solutions available from a number of vendors. MathML also satisfies
requirements in a number of highlyregulated industries, where documentation
must be in standardized formats. Because it is a standard that is not owned
by any one company, users of MathML will not be at the mercy of a single
vendor.
 Since MathML is part of the XML world, math can be handled as part of
a publisher's regular XMLbased production stream. This makes possible repurposing of
content (including math) for various media (web, paper, CDROM). Future XMLbased
technologies, such as structured searching, will also seamlessly apply to
MathML.
 MathML separates mathematical content from visual presentation. This
enables content providers to customize notational conventions, etc. by merely
changing a stylesheet and not the source document.
Although the authors of this report believe that the HTML+MathML Platform
provides huge benefits over other formats, they recognize that these formats may
still make sense in some applications. PDF is still a strong choice when exact typographic control is necessary,
when faithfulness to a printed version of a publication is a strong priority, or when
converting from legacy formats such as TeX. GIF images are still the best
choice when compatibility with the greatest number of browsers is paramount.
Static Math Doesn't Need to be so Static
It has been noted many times (e.g., our
"Strategies for Math on
the Web" [13]) that web documents containing math can be divided into two groups:
 Static Math: These are exemplified by technical or research papers that
are the web equivalent to their printed form. The main objective is for them
to simply be read.
 Dynamic Math: These are web pages that interact with the user. Examples
include online exams where answers are entered using an equation input control
(e.g., Design Science's WebEQ) and a page where an equation is graphed, allowing
numerical parameters to be entered and the graph to be updated accordingly.
While dynamic math can certainly add value to a publisher's content, it is
usually only meaningful for K12 education applications and can be quite costly
to develop. Most STM content is of the static math variety, consisting of online
versions of journals and textbooks. It is our thesis that the math in these
static math documents need not really be so static and, by making this math a
bit more dynamic using the power of MathML, the publisher can add value, thereby
making its content more attractive to consumers.
MathPlayer's RightClick Menu
One obvious reason to encode mathematics in a web page using MathML is so
that it can be rendered in a browser. MathML does have some advantages here over
other formats such as GIF images and PDF. However, because MathML represents
mathematical meaning (particularly with Content MathML), there is much more that
can be done than just displaying it.
MathPlayer, Design Science's MathML display engine for Internet Explorer,
features a rightclick menu containing a Copy command for copying an equation's
MathML to the Windows Clipboard, allowing it to be pasted into any application
that supports MathML. For example, an engineer viewing a web page presenting
mathematical formulas used in bridge design could paste them into Mathematica
and immediately use them in calculations for a new bridge.
Design Science expects to expand the set of commands available to readers in
future versions of MathPlayer. Possibilities include various "Open with ..."
commands, such as "Open with Mathematica", "Open with Maple", and "Open with
WebEQ". In the future, it may be possible to add a "Search for Similar
Equations" command that would search the web for papers with mathematics like
the clickedon equation, possibly helping a researcher get help in solving a
problem.
More Value than PDF
Many online research journals now publish using Adobe's PDF. This is fairly
easy to do as the document need only be designed once for both printed and
online publication. However, PDF does not add much value to the content.
Although the reader can copy the document's text, this is of limited interest.
If the document is published in HTML+MathML, the math now becomes useful and,
therefore, more desirable to the reader. We believe it is a good way for the STM
publisher to make their content stand out against its competition.
Focus: The Second International MathML Conference
MathML users, vendors, and supporters gathered at the Second International
MathML Conference in Chicago on June 2830 to hear presentations on the
expanding world of MathML technology. In this section, we will try to give the
reader an overview of what was presented at the conference along with our
interpretation of its significance. Of course, any such summary will reflect the
interests and biases of the authors. Many of the papers are available at the MathML
Conference web site [2]. We apologize to those authors whose work is not
mentioned here.
Tutorials
The first day of the conference was devoted to
tutorials [14]:
The tutorials were wellattended, indicating that MathML is not
just a research project but is beginning to be used in realworld applications.
MathML in Browsers
The recent arrival of browser support for MathML, principally via
Netscape/Mozilla, Internet Explorer + MathPlayer, and the Universal MathML Style
Sheet, was a subject for several papers as well as a topic for many
conversations held between sessions. Here are some high points:
 David Carlisle of NAG, an editor of the MathML Specification and of LaTeX
fame, presented his paper, "MathML
on the Web: Using XSLT to Enable CrossPlatform Support for XHTML and MathML
in Current Browsers". In this invited talk, David explained how his
Universal MathML Style Sheet (UMSS) adapts an XHTML+MathML document for
display within the user's particular browser. The UMSS associates an XSL
stylesheet with the web page containing MathML mathematics. Before the browser
displays the page, it invokes the attached stylesheet which detects the
browser and its installed MathML display technology and transforms the page's
content accordingly. The UMSS enables the author to publish in a single format
while, at the same time, allowing for readers with a variety of browsers and
MathML display technologies.
 Roger Sidje of the University of Queensland, and principal developer
of the MathML support in Mozilla and Netscape, gave an invited talk: "MathML
amidst Open Web Standards: Mozilla's Building Blocks for Today and Tomorrow".
Roger summarized recent events culminating in the availability of MathML
support in the Mozilla browser and in the presumably more mainstream Netscape 7
browser. Roger also explained that the Mozilla project was not simply a
browser but a content delivery platform that could be wrapped by
applicationspecific code. He then went on to describe how this might be of
use to the MathML community. This fits in well with our thesis, described in
more detail above, that MathML display in browsers is just the beginning and
that it enables much more in the way of adding value to online content.
 At the time of the conference, MathML support was missing in Mozilla for
the Macintosh platform. According to Roger Sidje, the missing piece was quite
small but, because he did not have access to a Mac and had no experience in
Mac programming, he could not easily supply this piece. This was distressing
news to many attendees, including the authors of this report, as the Mac is an
important platform, specially in education. At lunch on the second day of the
conference, representatives of Design Science and Wolfram Research both
offered to find a solution to this problem. Wolfram Research people offered to
make the first attempt and, we are happy to report, were ultimately
successful. As of this writing, support for MathML is now part of the
Macintosh builds of Mozilla, and Roger Sidje claims there is a very good chance
of it being included in the next release of Netscape 7.0.
 One of the authors of this report, Robert Miner of Design Science, and an
editor of the MathML Specification, presented "An Object Model for Dynamic
Math". In this presentation, Robert addressed the
problems of creating interactive, dynamic web pages using MathML. First, he
provided a taxonomy of dynamic math on the web applications and enumerated the
requirements implied by these applications. He then proposed a model
consisting of three collections of objects: Equations, EquationControls, and
MathServices. Finally, his prototype implementation was described. The kind of
applications Robert's presentation talks about are from the realm of dynamic
math on the web, as opposed to the static math on the web characterized by
online presentation of scientific research. However, as we described above in
our section on how MathML adds value to STM publishing, even static math can
have some notsostatic uses.
Content MathML
As has been covered in earlier editions of this report and elsewhere, MathML
consists of two complementary sublanguages,
Presentation
MathML and Content MathML [14]. Presentation MathML, as the name implies, is
primarily concerned with the formatting of mathematical notation rather than its
mathematical meaning. Content MathML, on the other hand, is primarily concerned
with mathematical meaning rather than formatting. It was expected that
conversions from one sublanguage to the other be possible but with some loss of
precision and information. (Such conversions have, in fact, been implemented.)
At the conference, the number of presentations devoted to Content MathML was
surprising. It was as if it had been designated as the theme of the conference
(it was not). On further reflection, perhaps this should not have been so
surprising as:
 Presentation MathML is essentially a rendering problem. As the "display of
MathML in a browser" problem is mostly solved, dealing with Presentation
MathML is largely a fait accompli.
 Content MathML is closer to the heart of what MathML is intended to supply
over other languages for describing math: it captures mathematical meaning and
can be used as an exchange format for applications where maintaining
mathematical meaning is paramount.
Although there were many presentations involving Content MathML, here are
some of the more memorable ones:
 Sam Dooley of IBM, and of Techexplorer fame, presented "Bringing
MathML Content and Presentation Markup to the Web with the IBM MathML
Expression Editor". In this paper, he described his prototype
interactive MathML editor, codenamed Zed. One of Zed's most important and
powerful features is a customizable editing mechanism for Content MathML.
The MathML community agrees that the association of mathematical notation
with mathematical meaning needs to be customizable within an editor due to
the openended nature of mathematics. This concept appears to have been
embodied in Zed's design and, as far as can be determined in a demo of a
prototype, appears to be heading in the right direction.
 A team from Rice University presented "Connexions: MathML and
Collaborative Curriculum Development in Engineering".
This paper describes The Connexions Project
[16], a "communitydriven collaborative knowledge creation and
dissemination project." This impressive project has created 600 "modules"
for teaching concepts in electrical and computer engineering, computer
science, and applied mathematics. At the core of this project is an attempt
to replace the traditional units of pedagogical content (principally college
textbooks) by smaller modules that teach a single concept or a closely
related set of concepts. Such modules can more easily be combined to form
the basis of a class or a book or an educational web site. They also are
conducive to the association of metadata, such as placement in an accepted
and wellunderstood domainspecific taxonomy (e.g., the twopart Latin species
names used in biology, the Mathematical Subject Classification of the AMS
[17]).
This work, and other work like it, signifies a departure from traditional
ways of creating educational content and, perhaps, represents the beginning
of a paradigm shift in higher education publishing.
 According to the OpenMath Society,
its author, OpenMath [18] is "an emerging standard for representing
mathematical objects with their semantics". Its relationship with MathML
could be described as taking over where Content MathML leaves off in
capturing mathematical meaning. It is expected that Content MathML will make
reference to OpenMath Content Dictionaries in order to make mathematical
meaning more explicit. OpenMath is a subject that, while not part of MathML,
is very important to the MathML community. While there were not any papers
specifically about OpenMath, it was the subject of a tutorial and a poster
presentation and was mentioned in many papers. Also, the OpenMath and MathML
communities overlap considerably as was reflected in the conference
attendance.
MathML Web Services
Web services are a hot topic in modern computing. They allow web applications
to exchange information, mostly using XMLbased languages. XML provides a level
of generality and independence that traditional proprietary formats do not. As
MathML is an XMLbased language and the W3Crecommended way to encode
mathematics, it is naturally brought into play whenever mathematics is part of
the information to be exchanged. Both the major vendors of computer algebra
systems (CAS), Wolfram Research (Mathematica)
[19] and Waterloo Maple (Maple) [20],
presented papers describing web services involving a browserbased front end
communicating with a CAS configured as a web service.
 "webMathematica: How to Deliver Computational and
Visualization Services from a Web Server"
 "Essential Ingredients for Mathematical Content Deployment on the
Web: The MapleNet Experience"
These efforts are significant for two reasons:
 This use of a browserbased interface interacting with a CAS on a server
is one of the primary examples of MathML use, as described in Robert Miner's
paper, "An Object
Model for Dynamic Math".
 It is an example of MathML use within the larger world of Web Services. As
there is a lot of attention being given by the computing industry to Web
Services, it signals the movement of MathML into areas other than education
and technical documentation.
It is interesting to note the broad range of research topics presented at the
conference, much of it taking place at universities. The University of Western
Ontario and the University of Bologna continue to be prominent in the amount of
MathML related research performed and the number of attendees sent. Research was
not limited to academic institutions, as can be seen in this list of interesting
research papers presented at the conference:
 "MathML in the MOWGLI Project", Andrea Asperti and Michael Kohlhase,
Università degli Studi di Bologna and Carnegie Mellon University: This paper
describes the MOWGLI
[21]
(Mathematics On the Web: Get it by Logic and Interfaces) project which
attempts to establish "best practice" in the use of MathML, OpenMath, and
various metadata standards in the context of publishing, digital libraries,
and computational applications.
 "ContentFaithful Transformations for MathML", Sandy Huerter, Igor
Rodionov, and Stephen Watt, The University of Western Ontario: This paper
addresses the ins and outs of conversion from Content MathML to Presentation
MathML while retaining the mathematical structure represented in the Content
MathML.
 "What's the Use? Analysis of RealWorld MathML and Web Browser Usage",
Andrew Hunt, Wolfram Research, Inc.: Statistics were gathered from Wolfram
Research's two web sites that contain MathML. Among the statistics reported
are browser type and the frequency of specific MathML tags and character
entities.
 "Acquisition of Content: MathML in an Academic Setting", Michael
Kohlhase, Matthew Szudzik, Dana Scott, Klaus Sutner, Andrea Kohlhase, and
Peter Jansen, Carnegie Mellon University: This paper reports on
The CCAPS Project [22]
project. Like the Connexions project, the CCaps
project explores the creation of a new way of packaging educational content
that gives more emphasis to the creation, storage, and retrieval of
educational units.
 "An
Interactive Mathematical Handwriting Recognizer for the Pocket PC", Bo
Wan and Stephen Watt, The University of Western Ontario: This interesting
paper reported on a project to create a realtime mathematical handwriting
recognizer on a small handheld computer. Although it was made clear that
the system was not yet useable, it was interesting to the audience as an
attempt to provide what is perhaps the holy grail of mathematics user
interfaces.
News Roundup
This section spotlights important developments that have been announced since
the most recent
edition of the Status Report was published in January, 2002 [4]. The list may
not be complete, and the authors apologize in advance for any omissions. Some of
these items are covered in more detail in the part of this report devoted to the
MathML Conference.
 MathML support is included in the Netscape 7.0 PR1 web browser. This means that many in the MathML community will
be able to get a browser that supports MathML via the better supported and
more widely available Netscape browser, rather than via Mozilla.
 The Macintosh version of Mozilla now supports MathML. This has been
a gaping hole in Mozilla's MathML support for some time. Now, due to the
efforts of Wolfram Research personnel, with Roger Sidje's assistance, the gap
has been filled. Roger feels that MathML support will be included in Netscape
7 for the Mac as well.
 MathPlayer 1.0 enables MathML support in Internet Explorer. Design
Science's MathPlayer
MathML display engine for Microsoft's Internet Explorer browser has been in
beta test since January 2002. As of this writing, beta 5 has just been
released. By the time you read this, the final version of MathPlayer 1.0
should be available for free download.
 MathType 5.1 [23] includes support for the Universal Math Style Sheet (UMSS)
and improved translation to MathML. Expected to be shipping by the time
you read this.
 MathML Central [24] introduced. Wolfram Research, makers of Mathematica,
introduced a web site that makes available several MathML tools: rendering
MathML, plotting MathML, etc. The purpose of these tools appears to be a sales
tool to demonstrate the power of Mathematica rather than something useful
directly.
 eCollege makes use of WebEQ in their latest course management system.
According to their
press releases
[25], their new eCollege AU+ product includes
an Equation Builder feature: "Powered by Design Science's WebEQ™ technology,
this tool enables users to build and edit mathematic equations through the
courseauthoring environment with oneclick access." See also [26].
[1] MathML, http://www.w3.org/Math;
[2] Second International
MathML Conference,
http://www.mathmlconference.org/2002;
[3] Adobe's Portable Document Format (PDF),
http://www.adobe.com/acrofamily/main.html;
[4] Math on the Web Status Report (all editions),
http://www.dessci.com/en/reference/webmath/status/;
[5] World Wide Web Consortium (W3C),
http://www.w3.org;
[6] MathPlayer,
http://www.dessci.com/en/products/mathplayer/;
[7] Microsoft Internet Explorer,
http://www.microsoft.com/windows/ie/default.asp;
[8] WebEQ, (formerly http://www.dessci.com/en/products/webeq/ since replaced by
MathFlow Components
http://www.dessci.com/en/products/mathflow/);
[9] Mozilla, http://www.mozilla.org;
[10] Netscape 7.0 Preview Release 1 (PR1),
http://channels.netscape.com/ns/browsers/7/default.jsp;
[11] Extensible Stylesheet Language
(XSL), http://www.w3.org/Style/XSL/;
[12] Universal Math Style Sheet (UMSS),
http://www.w3.org/Math/XSL/;
[13] "Strategies for Math on the Web",
http://www.dessci.com/en/reference/webmath/strategies.htm;
[14] Tutorials of the Second International MathML Conference
http://www.mathmlconference.org/2002/tutorials.html
[15] Presentation MathML and Content MathML,
http://www.w3.org/TR/MathML2/chapter2.html#fund_overview;
[16] Connexions Project, http://cnx.rice.edu/;
[17] Mathematical Subject Classification of the AMS,
http://www.ams.org/msc/;
[18] OpenMath, http://www.openmath.org/;
[19] Wolfram Research (Mathematica),
http://www.wolfram.com;
[20] Waterloo Maple (Maple),
http://www.maplesoft.com;
[21] The MOWGLI Project,
http://www.mowgli.cs.unibo.it;
[22] The CCAPS Project,
http://www2.cs.cmu.edu/~ccaps/;
[23] MathType,
http://www.dessci.com/en/products/mathtype/;
[24] MathML Central,
http://www.mathmlcentral.com/;
[25] eCollege AU+ press release,
http://www.ecollege.com/stories/press_08_14_02.html (no longer available)
[26] eCollege Equation Builder press release,
http://www.ecollege.com/stories/press_05_15_02.html (no longer available)
