A continuous based heuristic for the maximum clique problem. - Luana E. Gibbons; Donald W. Hearn; Panos M. Pardalos (Cliques, Coloring, and Satisfiability, 1993)

Continuous Characterizations of the Maximum Clique Problem. - Luana E. Gibbons; Donald W. Hearn; Panos M. Pardalos; Motakuri V. Ramana (Math. Oper. Res., 1997)