Resve A. Saleh Brian A. A. Antao Jaidip Singh Multilevel and mixed-domain simulation of analog circuits and systems. 68-82 1996 15 IEEE Trans. on CAD of Integrated Circuits and Systems 1 http://doi.ieeecomputersociety.org/10.1109/43.486273 db/journals/tcad/tcad15.html#SalehAS96