Constraint Hierarchies and Logic Programming. - Alan Borning; Michael J. Maher; Amy Martindale; Molly Wilson (ICLP, 1989)

Extending Hierarchical Constraint Logic Programming: Nonmonotonicity and Inter-Hierarchy Comparison. - Molly Wilson; Alan Borning (NACLP, 1989)

Constraint hierarchies and their applications. - Alan Borning; Bjørn N. Freeman-Benson; John Maloney; Molly Wilson (Compcon, 1991)

Constraint Hierarchies. - Alan Borning; Bjørn N. Freeman-Benson; Molly Wilson (LISP Symb. Comput., 1992)

Hierarchical Constraint Logic Programming. - Molly Wilson; Alan Borning (J. Log. Program., 1993)