@article{GDZPPN000363685,
title = {Lower Bounds on Moving a Ladder in Two and Three Dimensions.},
journal = {Discrete \& computational geometry},
volume = {3},
year = {1988},
pages = {197-218},
zbl = {0646.68059},
url = {http://dml.mathdoc.fr/item/GDZPPN000363685}
}
Ke, Y.; O'Rourke, Joseph. Lower Bounds on Moving a Ladder in Two and Three Dimensions.. Discrete & computational geometry, Tome 3 (1988) pp. 197-218. http://gdmltest.u-ga.fr/item/GDZPPN000363685/