Ramesh Krishnamurti Daya Ram Gaur Subir Kumar Ghosh Horst Sachs Berge's theorem for the maximum charge problem. 174-178 2006 3 Discrete Optimization 2 http://dx.doi.org/10.1016/j.disopt.2005.08.008 db/journals/disopt/disopt3.html#KrishnamurtiGGS06