Venkatesh Ramakrishnan Ernst Martin Witte Torsten Kempf David Kammler Gerd Ascheid Heinrich Meyr Marc Adrat Markus Antweiler http://arxiv.org/abs/0906.3313 2009 CoRR abs/0906.3313 db/journals/corr/corr0906.html#abs-0906-3313 informal publication