add citation information

README.md

@@ -47,10 +47,22 @@ Help & Documentation
   [_scrm's Wiki_](https://github.com/paulstaab/scrm/wiki).
 
 
+Citation
+======================
+Please cite the following article when using _scrm_ in a publication:
+
+> Paul R. Staab, Sha Zhu, Dirk Metzler and Gerton Lunter.
+> **scrm: efficiently simulating long sequences using the approximated coalescent
+> with recombination**. 
+> Bioinformatics (2015) 31 (10): 1680-1682.
+> [doi:10.1093/bioinformatics/btu861](http://bioinformatics.oxfordjournals.org/content/31/10/1680).
+
+
 Bug Reports
 =======================
-Please report problems with _scrm_ using its 
-[issue tracker](https://github.com/scrm/scrm-r/issues). 
+Please report any problems via the [issue tracker](https://github.com/scrm/scrm-r/issues)
+or via email to `develop (at) paulstaab (dot) de`.
+
 Please include the version you are using and the exact command that 
 causes the problem including seed (if applicable) in the report.
-Also, feel free to suggest features you would like to see in _scrm_ there.
+Also, feel free to suggest features there.