The Milnor Number and Deformations of Complex Curve Singularities. Gert-Martin Greuel; Ragnar Buchweitz — 1980 Inventiones mathematicae
The homological theory of maximal Cohen-Macaulay approximations Maurice Auslander; Ragnar-Olaf Buchweitz — 1989 Mémoires de la Société Mathématique de France
Lower bounds for Betti numbers Luchezar L. Avramov; Ragnar-Olaf Buchweitz — 1993 Compositio Mathematica