Youpyo Hong Peter A. Beerel Jerry R. Burch Kenneth L. McMillan Sibling-substitution-based BDD minimization using don't cares. 44-55 2000 19 IEEE Trans. on CAD of Integrated Circuits and Systems 1 http://doi.ieeecomputersociety.org/10.1109/43.822619 db/journals/tcad/tcad19.html#HongBBM00