@article{GDZPPN000364924, title = {Some Provably Hard Crossing Number Problems.}, journal = {Discrete \& computational geometry}, volume = {6}, year = {1991}, pages = {443-460}, zbl = {0765.68202}, url = {http://dml.mathdoc.fr/item/GDZPPN000364924} }
Bienstock, D. Some Provably Hard Crossing Number Problems.. Discrete & computational geometry, Tome 6 (1991) pp. 443-460. http://gdmltest.u-ga.fr/item/GDZPPN000364924/