Chong S. Rim Toshinobu Kashiwabara Kazuo Nakajima Exact algorithms for multilayer topological via minimization. 1165-1173 1989 8 IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. 11 https://doi.org/10.1109/43.41502 db/journals/tcad/tcad8.html#RimKN89