Rosso's form and quantized Kac Moody algebras. Anthony Joseph; Gail Letzter — 1996 Mathematische Zeitschrift
Verma module annihilators for quantized enveloping algebras Anthony Joseph; Gail Letzter — 1995 Annales scientifiques de l'École Normale Supérieure
Rings of differential operators over rational affine curves Gail Letzter; Leonid Makar-Limanov — 1990 Bulletin de la Société Mathématique de France