Paola Flocchini Alessandro Roncato Nicola Santoro Backward Consistency and Sense of Direction in Advanced Distributed Systems. 281-306 2003 32 SIAM J. Comput. 2 http://epubs.siam.org/sam-bin/dbq/article/37729 db/journals/siamcomp/siamcomp32.html#FlocchiniRS03