readme: move reference paper at the end

README.md

@@ -3,12 +3,6 @@ cim.py
 cim.py is a non-linear eigenvalue solver using the contour integral method
 proposed by W.-J. Beyn coupled with a [GetDP](http://getdp.info) formulation.
 
-Reference paper
----------------
-[W.-J., Beyn, "An integral method for solving nonlinear eigenvalue problems",
-Linear Algebra and its Applications, 2012,436.](
-https://doi.org/10.1016/j.laa.2011.03.030)
-
 Usage
 -----
 
@@ -101,6 +95,12 @@ Finally, don't forget to update your `PATH`, `PYTHONPATH` and `LD_LIBRARY_PATH`.
 
 Enjoy!
 
+Reference paper
+---------------
+[W.-J., Beyn, "An integral method for solving nonlinear eigenvalue problems",
+Linear Algebra and its Applications, 2012,436.](
+https://doi.org/10.1016/j.laa.2011.03.030)
+
 License
 -------
 Copyright (C) 2017 N. Marsic, F. Wolf, S. Schoeps and H. De Gersem,