Citation: Rr. Ashurov et Wn. Everitt, Linear quasi-differential operators in locally integrable spaces on the real line, P RS EDIN A, 130, 2000, pp. 671-698
Citation: Wn. Everitt et L. Markus, Complex symplectic geometry with applications to ordinary differential operators, T AM MATH S, 351(12), 1999, pp. 4905-4945