Sharad Malik Luciano Lavagno Robert K. Brayton Alberto L. Sangiovanni-Vincentelli Symbolic minimization of multilevel logic and the input encoding problem. 825-843 1992 11 IEEE Trans. on CAD of Integrated Circuits and Systems 7 http://doi.ieeecomputersociety.org/10.1109/43.144847 db/journals/tcad/tcad11.html#MalikLBS92