Duff, G. F. D. 1926- Partial differential equations/ G. F. D. Duff. - Toronto: University of Toronto Press, 1956. - x, 248 p.: diagrs., 24 cm. - Mathematical expositions no. 9. . Bibliography: p. [244]-245. LCCN: a 56004187 Nat. Bib. No.: GB56-4706 Subjects--Topical Terms: Differential equations, Partial. Dewey Class. No.: 515.35 / D855p