David A. Mix Barrington Chi-Jen Lu Peter Bro Miltersen Sven Skyum On Monotone Planar Circuits. 24- 1999 conf/coco/1999 IEEE Conference on Computational Complexity http://doi.ieeecomputersociety.org/10.1109/CCC.1999.766259 db/conf/coco/coco1999.html#BarringtonLMS99