Himanshu Thapliyal Hamid R. Arabnia Rajnish Bajpai Kamal K. Sharma Partial Reversible Gates(PRG) for Reversible BCD Arithmetic http://arxiv.org/abs/0711.2674 2007 CoRR abs/0711.2674 db/journals/corr/corr0711.html#abs-0711-2674 informal publication