Jeremy R. Tolbert Saibal Mukhopadhyay Accurate buffer modeling with slew propagation in subthreshold circuits. 91-96 2009 ISQED http://dx.doi.org/10.1109/ISQED.2009.4810275 conf/isqed/2009 db/conf/isqed/isqed2009.html#TolbertM09