Ioannis Papaefstathiou Theofanis Orphanoudakis George Kornaros Christopher Kachris Ioannis Mavroidis Aristides Nikologiannis http://arxiv.org/abs/0710.4813 2007 CoRR abs/0710.4813 db/journals/corr/corr0710.html#abs-0710-4813 informal publication