Jayram S. Thathachar On Separating the Read-k-Times Branching Program Hierarchy Electronic Colloquium on Computational Complexity (ECCC) 1998 2 5 db/journals/eccc/eccc5.html#ECCC-TR98-002 http://eccc.hpi-web.de/eccc-reports/1998/TR98-002/index.html