Gek Ling Chia C. L. Lee Crossing Numbers and Skewness of Some Generalized Petersen Graphs. 80-86 http://dx.doi.org/10.1007/978-3-540-30540-8_8 2003 conf/jcdcg/2003 IJCCGGT db/conf/jcdcg/ijccggt2003.html#ChiaL03