Petr Savický Detlef Sieling A Hierarchy Result for Read-Once Branching Programs with Restricted Parity Nondeterminism Electronic Colloquium on Computational Complexity (ECCC) 2001 8 17 db/journals/eccc/eccc8.html#ECCC-TR01-017 http://eccc.hpi-web.de/eccc-reports/2001/TR01-017/index.html