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<html>
<head>
<link rel="stylesheet" type="text/css" href="regina.css">
<title>Regina - Software for low-dimensional topology</title>
</head>
<body bgcolor="#FFFFFF" text="#000000"
link="#0000EE" vlink="#551A8B" alink="#FF0000">
<center>
<img src="title-outline.svg" height=160 vspace=10
alt="Regina: Software for low-dimensional topology">
</center>
<center>
<!--h4>Version 7.4.1 currently being uploaded (30 November 2025)</h4-->
<h4>Latest version: 7.4.1 (November 2025)</h4>
<!--Updated packages: 23 June 2023<br>
Updated documentation: 9 May 2022<br>
Updated packages: 10 December 2021<br>
Updated data: 31 May 2018></h4-->
<table class="contentswrapper" cellspacing=0>
<tbody>
<tr><th><a name="contents">Contents</a></th><th>C++/Python changes</th></tr>
<tr><td valign="top" rowspan=3>
<table class="contents" cellspacing=0><tbody>
<tr><td><a href="#news">News</a></td></tr>
<tr><td><a href="#whatis">What is Regina?</a></td></tr>
<tr><td><a href="#screenshots">Screenshots</a></td></tr>
<tr><td><a href="#download">Download</a></td></tr>
<tr><td><a href="#docs">Documentation</a></td></tr>
<tr><td><a href="#new">What's new in version 7.4.1?</a></td></tr>
<tr><td><a href="#announce">Release announcements</a></td></tr>
<tr><td><a href="#license">License and citation</a></td></tr>
<tr><td><a href="#contact">Contact</a></td></tr>
</tbody></table>
</td>
<td valign="top">
<table class="contents" cellspacing=0><tbody>
<tr><td><a href="api/recent.html">Keeping your code updated</a></td></tr>
<tr><td><a href="docs/regina7.html">Important changes in 7.x</a></td></tr>
</tbody></table>
</td></tr>
<tr><th>Other pages</th></tr>
<tr><td valign="top">
<table class="contents" cellspacing=0><tbody>
<tr><td><a href="data.html">Supporting data</a></td></tr>
<tr><td><a href="source.html">Building from source</a></td></tr>
<tr><td><a href="https://github.com/regina-normal/regina">GitHub repository</a></td></tr>
<tr><td><a href="bugs.html">Past important bugs</a></td></tr>
<tr><td><a href="docs/troubleshooting.html">Troubleshooting and FAQ</a></td></tr>
</tbody></table>
</td></tr>
</tbody>
</table>
</center>
<h2><a name="news">News</a></h2>
<p class="header">
<b>5 March 2026:</b>
The default branches for Regina's GitHub repositories have been renamed
from <tt>master</tt> to <tt>main</tt>.
You can update each of your local clones by running:
<div class="example"><p>
<tt>git branch -m master main<br>
git fetch origin<br>
git branch -u origin/main main<br>
git remote set-head origin -a</tt>
</p></div>
<p class="header">
<b>30 November 2025:</b>
Regina 7.4.1 is out!
This is a service release, and includes an
<a href="bugs.html#bcbuild">important bugfix</a> regarding
triangulated boundary components.
<a href="#new">Read about the changes</a>,
or just go ahead and <a href="#download">download it</a>.
<p class="header">
<b>29 August 2025:</b>
Regina 7.4 is out!
This is a big one.
<a href="#new">Read all about what's new</a> here.
<!--p class="header">
<b>17 July 2025:</b>
Packages are now live for Windows, Debian testing (trixie), and Arch Linux
(in addition to all the other packages that were available on release day).
Follow the <a href="#download">install links</a> for details.<-->
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="whatis">What is Regina?</a></h2>
Regina is a software package for low-dimensional topologists, with a focus on
3-manifold and 4-manifold triangulations, knots and links, normal surfaces,
and angle structures.
<p>
For 3-manifolds, it includes high-level tasks such as 3-sphere and unknot
recognition, connected sum decomposition and Hakenness testing, comes with a
rich database of census manifolds, and incorporates the SnapPea kernel for
working with hyperbolic manifolds. For 4-manifolds, it offers several
combinatorial and algebraic tools, as well as support for normal hypersurfaces.
For knots and links, Regina can perform combinatorial manipulation, compute
knot polynomials, handle virtual knots and links, and work with several
import/export formats.
<p>
Regina comes with a full graphical user interface, as well as Python bindings
and a low-level C++ programming interface.
<p>
See the users' handbook for a <a href="docs/featureset.html">detailed list
of features</a>.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="screenshots">Screenshots</a></h2>
Click on each thumbnail below for a full-sized version of the screenshot.
<p>
<table border=0>
<tr>
<td align=center><a href="shots/osx/1-triangulations.png">
<img srcset="shots/thumb/1-triangulations.png 1x, shots/thumb/1-triangulations@2x.png 2x, shots/thumb/1-triangulations@3x.png 3x" src="shots/thumb/1-triangulations.png"
hspace=5 align=middle border=0
alt="Screenshot thumbnail"></a></td>
<td align=center><a href="shots/osx/2-surfaces.png">
<img srcset="shots/thumb/2-surfaces.png 1x, shots/thumb/2-surfaces@2x.png 2x, shots/thumb/2-surfaces@3x.png 3x" src="shots/thumb/2-surfaces.png"
hspace=5 align=middle border=0
alt="Screenshot thumbnail"></a></td>
</tr>
<tr>
<td align="center">Studying 3-manifold<br>triangulations</td>
<td align="center">Normal surfaces and<br>angle structures</td>
</tr>
<tr>
<td align=center><a href="shots/osx/3-links.png">
<img srcset="shots/thumb/3-links.png 1x, shots/thumb/3-links@2x.png 2x, shots/thumb/3-links@3x.png 3x" src="shots/thumb/3-links.png"
hspace=5 align=middle border=0
alt="Screenshot thumbnail"></a></td>
<td align=center><a href="shots/osx/4-python.png">
<img srcset="shots/thumb/4-python.png 1x, shots/thumb/4-python@2x.png 2x, shots/thumb/4-python@3x.png 3x" src="shots/thumb/4-python.png"
hspace=5 align=middle border=0
alt="Screenshot thumbnail"></a></td>
</tr>
<tr>
<td align="center">Knots and<br>links</td>
<td align="center">In-built Python<br>scripting</td>
</tr>
</table>
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="download">Download</a></h2>
<p>
The following downloads are available:
<p>
<table class="contentswrapper" cellspacing=0>
<tbody>
<tr><td valign="top">
<table class="contents" cellspacing=0><tbody>
<tr><td><a href="#macos">Mac</a></td></tr>
<tr><td><a href="#windows">Windows</a></td></tr>
<tr><td><a href="#linux">GNU/Linux</a></td></tr>
<tr><td><a href="#sage">PyPI / SageMath</a></td></tr>
<tr><td><a href="#ios">iPad</a></td></tr>
<tr><td><a href="#source">Source code</a></td></tr>
</tbody></table>
</td></tr>
</tbody>
</table>
<p>
All direct downloads come with
<a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/SHA1SUMS-signed.txt">SHA-1 checksums</a>
and
<a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/SHA256SUMS-signed.txt">SHA-256 checksums</a>,
signed with <a href="https://people.debian.org/~bab/regina-key.txt">Ben Burton's GPG key</a>.
<p>
If you encounter any problems when you run Regina, you can check the
<a href="docs/troubleshooting.html">troubleshooting page</a> to
see if your problem is discussed there. You also most welcome
to <a href="#contact">contact us</a> for help.
<a name="macos"><h4 class="divide">Mac</h4></a>
Regina runs natively on both Intel and Apple Silicon machines.
It ships with its own copy of Python 3, which is bundled inside
Regina's macOS app.
<p>
You can download Regina either from this website, or via the App Store
(for free of course).
Not sure which? Start with the App Store version (but read below).
<p>
<blockquote><table cellspacing=0 border=0 align=center class="data"><tbody>
<tr><th class="first" colspan=2>macOS version</th>
<th>Website download</th>
<th>App Store</th></tr>
<tr><td class="firstjoin">Tahoe (26)<br>
Sequoia (15)<br>
Sonoma (14)
</td>
<td><img srcset="osicons/os_macosx.png 1x, osicons/os_macosx@2x.png 2x" src="osicons/os_macosx.png" border=0 hspace=5></td>
<td align="center"><a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/Regina-7.4.1_py39.dmg">Download here</a></td>
<td><a href="https://itunes.apple.com/us/app/regina-for-3-manifolds/id1160053348?mt=8"><img src="ios/Download_on_the_Mac_App_Store_Badge_US-UK_RGB_wht_092917.svg" alt="Download on the Mac App Store" border=0 hspace=10 vspace=10/></a></td>
</tr>
</tbody></table>
</blockquote>
<p>
There are some minor differences between the website and App Store versions.
The App Store version:
<ul>
<li>means that macOS will notify you of upgrades;</li>
<li>is sandboxed for extra security, which limits file access through
Python and the command-line tools (see below).</li>
</ul>
<p>
Sandboxing is a security measure that comes with all App Store downloads:
it ensures that apps only access files that you explicitly choose
through the graphical file dialogs (<i>Open</i>, <i>Save</i>, etc.).
For Regina, this means that when you open a Python console or
run command-line tools (<tt>regina-python</tt>, <tt>regfiledump</tt>, etc.),
the <b>only personal files you can access are those in your
<tt>Downloads</tt> folder</b>. You can still access world-readable files,
such as those in your <tt>Applications</tt> folder.
<p class="header">
<b>Regarding security:</b>
<ul>
<li>The website download is cryptographically signed with Ben Burton's Apple
developer certificate, and has been pre-screened (notarised) by Apple.
macOS will verify all of this when you first try to run Regina.
You should see a message like
<i>“Regina is an app downloaded from the internet…
Apple checked it for malicious software and none was detected.”</i>.</li>
<li>The App Store version has been screened by both machines and humans at
Apple, and has a chain of cryptographic signatures that certify this.
These signatures will be verified when you install Regina via the
App Store.</li>
</ul>
<a name="windows"><h4 class="divide">Windows</h4></a>
Regina on Windows uses a standard point-and-click installer.
<p>
Regina now <b>only supports 64-bit Windows</b>,
and only on Intel/AMD64 chipsets (i.e., the <tt>x64</tt> architecture).
Most modern Windows installations are of this type,
and this is almost certainly the version that you want.
<p>
If your machine has an ARM64 chipset (e.g., you have a Mac with
Apple Silicon), you will need to run Regina under a different operating
system (e.g., macOS or GNU/Linux).
<p>
<blockquote><table cellspacing=0 border=0 align=center class="data"><tbody>
<tr><th class="first" colspan=2>Windows version</th>
<th>Architectures</th>
<th>Installer</th></tr>
<tr><td class="firstjoin">Windows 11<br>Windows 10</td>
<td><img srcset="osicons/os_win_other.png 1x, osicons/os_win_other@2x.png 2x" src="osicons/os_win_other.png" border=0 hspace=5></td>
<td><tt>x64</tt></td>
<td align="center"><a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/Regina-7.4.1-x86_64.msi">Download</a></td>
</tr>
</tbody></table>
</blockquote>
<p class="header">
<b>Regarding security:</b>
<ul>
<li>When downloading or running the installer you may see a security warning,
such as <i>“Microsoft Defender SmartScreen prevented an
unrecognized app from starting…”</i>, or a message that
<i>“Microsoft Defender SmartScreen couldn't verify if this file
is safe…”</i>.
This is because Microsoft has not added Regina to its database of
known applications.
Click <i>More info</i> or look for a drop-down box with more options,
and you should be able to run the installer anyway.</li>
<li>If you wish to verify the integrity of the download, you can compare
checksums against the expected
<a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/SHA1SUMS-signed.txt">SHA-1 checksums</a>
and
<a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/SHA256SUMS-signed.txt">SHA-256 checksums</a>,
which are cryptographically signed with
<a href="https://people.debian.org/~bab/regina-key.txt">Ben Burton's GPG key</a>.</li>
</ul>
<a name="linux"><h4 class="divide">GNU/Linux</h4></a>
You can download ready-made packages for several GNU/Linux distributions
through Regina's online package repositorites.
These repositories integrate with your native package manager
(<tt>apt</tt>, <tt>dnf/yum</tt>, <tt>zypper</tt>, etc.)
to help you keep Regina up-to-date automatically.
<p>
For instructions on setting up Regina's package repositories,
click on the <i>Install</i> link for your system in the table below.
<p>
Regina's GNU/Linux packages are named <b>regina-normal</b> (to avoid conflicting
with the <a href="http://regina-rexx.sourceforge.net/">other Regina</a>).
<p>
<blockquote><table cellspacing=0 border=0 align=center class="data"><tbody>
<tr><th class="first" colspan=2>Distribution</th>
<th>Versions</th>
<th>Architectures</th>
<th>Instructions</th>
</tr>
<tr><td rowspan=1 class="firstjoin">Arch Linux</td>
<td rowspan=1><img srcset="osicons/os_archlinux.png 1x, osicons/os_archlinux@2x.png 2x" src="osicons/os_archlinux.png" border=0 hspace=5></td>
<td>Rolling release</td>
<td><tt>x86_64</tt></td>
<td align="center"><a href="install/archlinux.html">Install</a></td>
</tr>
<tr><td rowspan=2 class="altfirstjoin">Debian</td>
<td rowspan=2 class="alt"><img srcset="osicons/os_debian.png 1x, osicons/os_debian@2x.png 2x" src="osicons/os_debian.png" border=0 hspace=5></td>
<td class="alt">13.x (trixie)<br>12.x (bookworm)</td>
<td class="alt"><tt>amd64</tt><br><tt>arm64</tt><br>
<tt>i386</tt> (bookworm only)</td>
<td align="center" rowspan=2 class="alt"><a href="install/debian.html">Install</a></td>
</tr>
<tr>
<td class="alt">unstable (sid)</td>
<td class="alt">Everything</td>
</tr>
<tr><td rowspan=1 class="firstjoin">Fedora</td>
<td rowspan=1><img srcset="osicons/os_fedora.png 1x, osicons/os_fedora@2x.png 2x" src="osicons/os_fedora.png" border=0 hspace=5></td>
<td>43<br>42<br>41</td>
<td><tt>aarch64</tt><br><tt>x86_64</tt></td>
<td align="center" rowspan=1><a href="install/fedora.html">Install</a></td>
</tr>
<tr><td rowspan=1 class="altfirstjoin">openSUSE</td>
<td rowspan=1 class="alt"><img srcset="osicons/os_opensuse.png 1x, osicons/os_opensuse@2x.png 2x" src="osicons/os_opensuse.png" border=0 hspace=5></td>
<td class="alt">Leap 16.0<br>Leap 15.6</td>
<td class="alt"><tt>aarch64</tt><br><tt>x86_64</tt></td>
<td class="alt" align="center"><a href="install/opensuse.html">Install</a></td>
</tr>
<tr><td rowspan=1 class="firstjoin">Ubuntu</td>
<td rowspan=1><img srcset="osicons/os_ubuntu.png 1x, osicons/os_ubuntu@2x.png 2x" src="osicons/os_ubuntu.png" border=0 hspace=5></td>
<td>25.10 (questing)<br>25.04 (plucky)<br>24.04 LTS (noble)</td>
<td><tt>amd64</tt><br><tt>arm64</tt></td>
<td align="center" rowspan=1><a href="install/ubuntu.html">Install</a></td>
</tr>
</tbody></table></blockquote>
<p class="header">
<b>Architectures:</b>
<ul><li>
You do not need to know what architecture you have; the online
repositories will work this out for you automatically.
</li>
<li>
For reference, <tt>amd64</tt>/<tt>x86_64</tt> refers to 64-bit Intel machines,
<tt>arm64</tt>/<tt>aarch64</tt> refers to 64-bit ARM machines
(including Apple Silicon), and
<tt>i386</tt> refers to very old 32-bit Intel machines.
Together these cover almost any typical desktop or laptop nowadays.
</li>
<li>
If you have a more exotic chipset that is not in the table above, you can try
downloading the <tt>regina-normal</tt> source package (which is provided for all
distributions above except for Arch Linux), and use this to build a
binary package yourself (e.g., using <tt>debuild</tt> or <tt>rpmbuild</tt>).
Alternatively, if you really want a ready-made binary package, you could try
the <a href="install/debian.html#unstable">Debian unstable packages</a>,
which are built for <i>every</i> architecture in Debian.
</li></ul>
<p class="header">
<b>For older versions of GNU/Linux:</b>
<ul><li>
If your distribution is in the table above but your version is
too old, then your version of GNU/Linux may have passed its end-of-life.
This is a <b>security risk</b>, since most distributions do not
provide security updates for old (end-of-life) versions.
You should seriously consider <b>upgrading your machine</b>.
</li></ul>
<p class="header">
<b>For newer versions of GNU/Linux:</b>
<ul><li>
If your distribution is in the table above but your version is
too new, then drop <a href="http://www.maths.uq.edu.au/~bab/">Ben</a>
an email and he should be able to upload a package for you.
Otherwise you can always build from source (see below).
</li></ul>
<p class="header">
<b>For other GNU/Linux distributions:</b>
<ul><li>
If you are using some other distribution (e.g., RedHat, Slackware, …),
then you will need to <a href="#source">build Regina from source</a>.
</li></ul>
<p class="header">
<b>Regarding security:</b>
<ul>
<li>All of Regina's GNU/Linux repositories use cryptographic signatures to
verify the integrity of the packages. Follow the appropriate <i>Install</i>
link above for details.</li>
</ul>
<a name="sage"><h4 class="divide">PyPI / SageMath</h4></a>
Marc Culler, Nathan Dunfield and Matthias Goerner have
kindly prepared a PyPI package that allows
Regina to be used with SageMath.
This includes the Python interface to Regina's mathematical engine,
but does not include Regina's graphical user interface or
command-line tools.
<p>
<blockquote><table cellspacing=0 border=0 align=center class="data"><tbody>
<tr><th class="first" colspan=2>System</th><th>Instructions</th></tr>
<tr><td class="firstjoin">PyPI</td>
<td><img srcset="osicons/sage.png 1x, osicons/sage@2x.png 2x" src="osicons/sage.png" border=0 hspace=5 vspace=5/></td>
<td align="center"><a href="https://github.com/3-manifolds/regina_wheels/">Install</a></td>
</tr>
</tbody></table>
</blockquote>
<p>
Of course, whilst the packages are written to work with any modern version
of SageMath, your experiences might vary (particular with an older SageMath
and/or operating system). Follow the instructions link above for details.
<a name="ios"><h4 class="divide">iPad</h4></a>
The iPad app is currently in hiatus. It has not been updated since before the
pandemic began, and there is a lot of rewriting to do.
Hopefully Ben will have time to do this some time during 2025.
<!--
The iPad app offers most of Regina's functionality (<b>now including
Python scripting!</b>), but not all. For
example, the iPad version does not support some of the more exotic
import/export formats, and some mathematical functions are only
accessible through Python (such as isomorphism testing, or manifolds of
dimension ≥ 5).
If you need these features then please download one of the
desktop versions listed above.
<p>
<blockquote><table cellspacing=0 border=0 align=center class="data"><tbody>
<tr><th class="first">iOS Version</th><th>Installer</th></tr>
<tr><td class="first">iOS 8 and above</td>
<td align="center"><a href="https://itunes.apple.com/us/app/regina-for-3-manifolds/id925244528?mt=8"><img src="ios/Download_on_the_App_Store_Badge_US-UK_RGB_wht_092917.svg" alt="Download on the App Store" border=0 hspace=10 vspace=10/></a></td>
</tr>
</tbody></table>
</blockquote-->
<a name="source"><h4 class="divide">Source code</h4></a>
<p>
For other systems not listed above, you will need to build Regina
from its source code.
<p>
You can <a href="https://github.com/regina-normal/regina/releases/download/regina-7.4.1/regina-7.4.1.tar.gz">download the source code here</a>.
<p>
Please see the <a href="source.html">separate page on building Regina</a>
for instructions on how to build Regina and
what libraries and tools you will need to have installed.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="docs">Documentation</a></h2>
Regina comes with rich documentation for both users and developers.
<h4>Users' Handbook</h4>
The Regina Handbook is full of screenshots, and walks you through the
different things that Regina can do.
<p>
You can read the handbook from within Regina by selecting
<i>Help</i> → <i>Regina Handbook</i>
from the menu. You can also
<a href="docs/index.html">read it here online</a>.
<h4>Python/C++ API Documentation</h4>
If you are doing Python scripting or C++ programming with Regina,
there is extensive API documentation for Regina's mathematical
engine. This describes the various objects, classes and functions that
Regina makes available to you.
<p>
You can read the API documentation by:
<ul>
<li>selecting <i>Help</i> → <i>Python API Reference</i>
from the menu;</li>
<li>reading it <a href="engine-docs/index.html">here online</a>;</li>
<li>getting inline help directly within Python via docstrings
(but please <a href="docs/python-docs.html">see the handbook</a> for the
limits of what these docstrings can and cannot provide).</li>
</ul>
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="new">What's new in version 7.4.1?</a></h2>
<p>
<h4>Regina 7.4.1</h4>
<p>
This is a service release to fix some important bugs, and to support
additional build environments. In particular:
</p>
<ul>
<li>Fixes a serious (and very old) bug that occurred when triangulating
a real boundary component. In short, the new triangulation of the
original boundary component could have had inconsistencies in the
labelling of its own lower-dimensional faces. Ideal boundaries were
not affected. For a detailed discussion of how this might have
affected you, see the <a href="bugs.html#bcbuild">bugs page</a>.</li>
<li>Fixes a bug in Katie's quadricolour search routine, which would cause
a segfault for certain inputs.</li>
<li>Adds a few missing Python bindings for triangulations in higher
dimensions.</li>
</ul>
<p>
<h4>Regina 7.4</h4>
<p>
In case you missed it, Regina 7.4 (August 2025) added many new features:
<ul>
<li>Now supports virtual knots and links, with new invariants such as
odd writhe, arrow polynomials, affine index polynomials, and
extended groups.</li>
<li>Several new constructions, such as Whitehead doubles over links,
doubling triangulations over their boundaries, and many new
out-of-the-box example triangulations and links.</li>
<li>Several new operations on triangulations and link diagrams, including
improving treewidth, truncating individual vertices in 3-D, and more
elementary moves in more dimensions.</li>
<li>New invariants and properties for link diagrams, including Alexander
polynomials, Seifert circles, and connected diagram components.</li>
<li>Significantly better simplification for 4-D triangulations, including
Rhuaidi Burke's “up-side-down” simplification heuristics.</li>
<li>Text codes for link diagrams now include signed Gauss codes, plus an
extension of Regina's knot signatures to multiple-component links.</li>
<li>You can now lock top-dimensional simplices and/or their facets in a
triangulation, to prevent these from being modified during operations
such as simplification or elementary moves. Locks are also encoded
as part of the isomorphism signature.</li>
<li>Gave the graphical user interface a general glow-up, and added
initial support for multithreaded computations.</li>
<li>The tool DGT is now called Katie, and can now work with 1-handles
(thanks again to Rhuaidi Burke).</li>
<li>New command-line tool regina-helper, which can do things like create
Makefiles and run the test suite.</li>
<li>Fixes an occasional problem where the “try harder” option for
simplifying triangulations could make the user interface crash.</li>
<li>Many, many other smaller features and optimisations.</li>
</ul>
<p>
Also, the build requirements have changed: Regina now uses C++20 (not C++17),
the GUI now requires Qt 6.x, the API docs now require
Doxygen ≥ 1.9.2, and you no longer need
Jansson, Popt or CppUnit.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="announce">Release announcements</a></h2>
The old SourceForge mailing lists have now been decommissioned.
<p>
To be notified of new releases, you can instead subscribe to Regina's releases
directly on GitHub. See the
<a href="https://regina-normal.github.io/docs/services.html">Regina Handbook</a>
for details.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="license">License and citation</a></h2>
The primary developers of Regina are
<a href="http://www.maths.uq.edu.au/~bab/">Benjamin Burton</a>,
<a href="http://rybu.org/">Ryan Budney</a>, and
<a href="http://ewpettersson.se/">William Pettersson</a>.
<p>
Many others have been of assistance with this project, be it through
time, knowledge, testing or code. Please see the
<a href="docs/credits.html">full list of acknowledgements</a>
in the users' handbook.
<h4>Citation</h4>
If you find Regina useful in your research, please consider citing it as
you would any other paper that you use. A suggested form of reference is:
<blockquote>
Benjamin A. Burton, Ryan Budney, William Pettersson, et al.,<br>
<i>Regina: Software for low-dimensional topology</i>,<br>
http://regina-normal.github.io/, 1999–2025.
</blockquote>
Or, in BibTeX:
<blockquote><pre>
@misc{regina,
author = {Benjamin A. Burton and Ryan Budney and William Pettersson and others},
title = {Regina: Software for low-dimensional topology},
howpublished = {{\tt http://\allowbreak regina-normal.\allowbreak github.\allowbreak io/}},
year = {1999--2025}}
</blockquote></pre>
<h4>Copying and modification</h4>
Regina is copyright © 1999–2025, The Regina development team.
<p>
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
<p>
Some of this code comes with additional permissions, which allow it
to be distributed through online repositories such as Apple's App Store
or Google Play. See the
<a href="docs/license.html">full license</a> in the users' handbook
for details.
<p>
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
<p>
You should have received a copy of the GNU General Public License along
with this program; if not, see
<a href="https://www.gnu.org/licenses/">https://www.gnu.org/licenses/</a>.
<h4>Detailed license</h4>
Regina includes portions of external software for specialised tasks
(such as code from SnapPea and SnapPy for some geometric calculations,
and code from Normaliz for computing Hilbert bases).
<p>
For complete license details, including the full GNU General Public
License and information on external software that Regina uses,
see the
<a href="docs/license.html">full license</a> in the users' handbook.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="contact">Contact</a></h2>
If you have any suggestions, problems, bugs, wishes, frustrations or
otherwise miscellaneous comments, we would <i>really</i> love to hear
them. This program is permanently under development and we would like to
know what people want out of it.
<p>
If you have written your own extensions that you think could be
worth putting in the main release, please do write and let us know.
<p>
Even if you have no comments to make, it's always nice to hear
from people using Regina, even if it's just to say hi.
We're always interested to hear how this software is being used.
<p>
You can contact us by email: our websites are linked to our names in the
<a href="#license">author list above</a>.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
<h2><a name="privacy">Privacy policy</a></h2>
Regina does not collect any data.
<p>
<i><a href="#contents">(Back to contents...)</a></i>
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