1. On monotone paths among obstacles with applications to planning assemblies;Arkin;Proc. 5th ACM Symp. on Computational Geometry,1989
2. Computers and Intractability, A Guide to the Theory of NP-Completeness;Garey,1979
3. On translating a set of rectangles;Guibas,1983
4. Sequences;Halberstam,1983