Pierre-Yves Calland Anne Mignotte Olivier Peyran Yves Robert Frédéric Vivien Retiming DAGs [direct acyclic graph]. 1319-1325 1998 17 IEEE Trans. on CAD of Integrated Circuits and Systems 12 http://doi.ieeecomputersociety.org/10.1109/43.736571 db/journals/tcad/tcad17.html#CallandMPRV98