@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/