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README.md

+<!--
+SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file LICENSE.md in module root
+SPDX-License-Identifier: LGPL-2.1-or-later
+-->
+
+# dune-uggrid
+
+This is a fork of the old [UG](https://doi.org/10.1007/s007910050003)
+finite element software, wrapped as a Dune module, and stripped of everything
+but the grid data structure. You need this module if you want to use the `UGGrid`
+grid implementation from the `dune-grid` module.
+
+To use this module, simply have it available when building `dune-grid`.
+The Dune build system will then pick it up when building `dune-grid`,
+and the `UGGrid` grid implementation becomes available.
+
+## Features
+
+The `UGGrid` grid data structure is very powerful and flexible.  Its main features are:
+
+* Unstructured two- and three-dimensional grids
+* Grids with more than one element type: triangles and quadrilaterals in 2d,
+  tetrahedra, hexahedra, prisms and pyramids in 3d
+* Adaptive red-green refinement, and nonconforming refinement
+* Anisotropic refinement
+* Distributed grids on large numbers of processes, connected by MPI
+* Free-form domain boundaries:  Individual grids always have polyhedral
+  boundaries, but refining the grids will approximate the actual
+  (free-form) boundary better and better.
+
+The features of `UGGrid` are described in more detail in the
+[Dune book](https://link.springer.com/book/10.1007/978-3-030-59702-3).
+
+## Planned features
+
+The following features are natural next steps in the development
+of `dune-uggrid`.
+
+* Checkpointing: Save the entire grid hierarchy to a file,
+  and read it back in again.
+* Direct construction of distributed grids (instead of constructing
+  the grid on rank 0 and then distributing)
+* Two-dimensional grids in a three-dimensional world
+
+## Releases
+
+Although technically not a "Dune core module",
+`dune-uggrid` is released together with the Dune core modules.
+Starting with version 2.10 you can find `dune-uggrid` release
+tarballs at the [same site](https://dune-project.org/releases/)
+as the Dune core module releases.
+
+Older release tarballs can be found at the following links:
+
+<table>
+<tr>
+  <th>version</th>
+  <th>source</th>
+  <th>signature</th>
+</tr>
+<tr>
+  <td>2.9.1</td>
+  <td><a href="https://dune-project.org/download/2.9.1/dune-uggrid-2.9.1.tar.gz" download>dune-uggrid-2.9.1.tar.gz</a></td>
+  <td><a href="https://dune-project.org/download/2.9.1/dune-uggrid-2.9.1.tar.gz.asc" download>dune-uggrid-2.9.1.tar.gz.asc</a></td>
+</tr>
+<tr>
+  <td>2.8.0</td>
+  <td><a href="https://dune-project.org/download/2.8.0/dune-uggrid-2.8.0.tar.gz" download>dune-uggrid-2.8.0.tar.gz</a></td>
+  <td><a href="https://dune-project.org/download/2.8.0/dune-uggrid-2.8.0.tar.gz.asc" download>dune-uggrid-2.8.0.tar.gz.asc</a></td>
+</tr>
+</table>
+
+## Maintainer
+
+The `dune-uggrid` module is currently maintained by [Oliver Sander](https://tu-dresden.de/mn/math/numerik/sander).