Andrej Bogdanov Kenji Obata Luca Trevisan A Lower Bound for Testing 3-Colorability in Bounded-Degree Graphs. 93-102 2002 conf/focs/2002 FOCS http://doi.ieeecomputersociety.org/10.1109/SFCS.2002.1181886 db/conf/focs/focs2002.html#BogdanovOT02