Kei Uchizawa Takao Nishizeki Eiji Takimoto Energy Complexity and Depth of Threshold Circuits. 335-345 2009 FCT http://dx.doi.org/10.1007/978-3-642-03409-1_30 conf/fct/2009 db/conf/fct/fct2009.html#UchizawaNT09