Alain Daurat Yan Gérard Maurice Nivat Some necessary clarifications about the chords' problem and the Partial Digest Problem. 432-436 2005 347 Theor. Comput. Sci. 1-2 http://dx.doi.org/10.1016/j.tcs.2005.05.021 db/journals/tcs/tcs347.html#DauratGN05