@article{DCG_1987__2_131022,
     author = {Micha Sharir and D. Leven},
     title = {On the {Number} of {Critical} {Free} {Contacts} of a {Convex} {Polygonal} {Object} {Moving} in {Two-Dimensional} {Polygonal} {Space.}},
     journal = {Discrete & computational geometry},
     pages = {255--270},
     publisher = {mathdoc},
     volume = {2},
     year = {1987},
     zbl = {0616.52009},
     url = {http://geodesic.mathdoc.fr/item/DCG_1987__2_131022/}
}