@article{DCG_1991__6_4_131170,
     author = {D. Bienstock},
     title = {Some {Provably} {Hard} {Crossing} {Number} {Problems.}},
     journal = {Discrete & computational geometry},
     pages = {443--460},
     publisher = {mathdoc},
     volume = {6},
     number = {4},
     year = {1991},
     zbl = {0765.68202},
     url = {http://geodesic.mathdoc.fr/item/DCG_1991__6_4_131170/}
}