Bhavani Shankar Prasant Gopal Kannan Srinathan C. Pandu Rangan Unconditionally reliable message transmission in directed networks. 1048-1055 2008 SODA http://doi.acm.org/10.1145/1347082.1347197 conf/soda/2008 db/conf/soda/soda2008.html#ShankarGSR08