update README with citation requirements

README.md

@@ -22,7 +22,11 @@ You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 Author: Antoine C.D. Hoffmann
-Publication: Hoffmann, A., Frei, B., & Ricci, P. (2023). Gyrokinetic simulations of plasma turbulence in a Z-pinch using a moment-based approach and advanced collision operators. Journal of Plasma Physics, 89(2), 905890214. doi:10.1017/S0022377823000284
+
+# Citing GYACOMO
+If you use GYACOMO in your work, please cite the following paper: 
+
+Hoffmann, A., Frei, B., & Ricci, P. (2023). Gyrokinetic simulations of plasma turbulence in a Z-pinch using a moment-based approach and advanced collision operators. Journal of Plasma Physics, 89(2), 905890214. doi:10.1017/S0022377823000284
 
 # How to compile and run GYACOMO