Update documentation ref/example (#470)

* Update documentation ref/example

* link preprint
* link benchmark collection

Author: dweindl

doc/example.rst

@@ -10,3 +10,6 @@ The following examples should help to get a better idea of how to use the PEtab
 
    example/example_petablint.ipynb
    example/example_visualization.ipynb
+
+Examples of systems biology parameter estimation problems specified in PEtab
+can be found in the `systems biology benchmark model collection <https://github.com/Benchmarking-Initiative/Benchmark-Models-PEtab>`_.

doc/how_to_cite.rst

@@ -0,0 +1,17 @@
+.. _how_to_cite:
+
+How to cite
+===========
+
+Help us to promote PEtab: When using PEtab, please cite our `preprint <https://arxiv.org/abs/2004.01154v4>`_:
+
+.. code-block:: latex
+
+    @misc{schmiester2020petab,
+          title={PEtab -- interoperable specification of parameter estimation problems in systems biology},
+          author={Leonard Schmiester and Yannik Schälte and Frank T. Bergmann and Tacio Camba and Erika Dudkin and Janine Egert and Fabian Fröhlich and Lara Fuhrmann and Adrian L. Hauber and Svenja Kemmer and Polina Lakrisenko and Carolin Loos and Simon Merkt and Wolfgang Müller and Dilan Pathirana and Elba Raimúndez and Lukas Refisch and Marcus Rosenblatt and Paul L. Stapor and Philipp Städter and Dantong Wang and Franz-Georg Wieland and Julio R. Banga and Jens Timmer and Alejandro F. Villaverde and Sven Sahle and Clemens Kreutz and Jan Hasenauer and Daniel Weindl},
+          year={2020},
+          eprint={2004.01154},
+          archivePrefix={arXiv},
+          primaryClass={q-bio.QM}
+    }

doc/index.rst

@@ -18,6 +18,7 @@
    :caption: About
 
    Changelog <CHANGELOG.md>
+   how_to_cite
    license
    logo/LICENSE.md