Michael Alekhnovich Jan Johannsen Toniann Pitassi Alasdair Urquhart An Exponential Separation between Regular and General Resolution. 81-102 2007 3 Theory of Computing 1 http://dx.doi.org/10.4086/toc.2007.v003a005 db/journals/toc/toc3.html#AlekhnovichJPU07