Jerzy W. Jaromczyk Grzegorz Swiatek A Theory of Even Functionals and Their Algorithmic Applications. 126-136 1993 conf/icalp/1993 ICALP db/conf/icalp/icalp93.html#JaromczykS93 http://dx.doi.org/10.1007/3-540-56939-1_67