Update README.md

Author: Mikolaj Feliks

README.md

@@ -23,7 +23,7 @@ The key features of the module include:
   * Close integration with pDynamo
 
 More information about the theoretical methods and algorithms used by Pcetk can be found
-in our article:
+in our article:<br />
 Feliks, M.; Field, M. "*Pcetk*: A pDynamo-based Toolkit for Protonation State Calculations in Proteins."
 *J. Chem. Inf. Model.* **2015**, *55*, pp. 2288-2296 (http://dx.doi.org/10.1021/acs.jcim.5b00262)