Systems of Set Constraints with Negative Constraints are NEXPTIME-Complete - Kjartan Stefánsson (LICS, 1994)

Newtonian Graphs, Riemann Surfaces and Computation. - Kjartan Stefánsson (1995)

Computing the Newtonian Graph. - Dexter Kozen; Kjartan Stefánsson (J. Symb. Comput., 1997)