Theory of Differential Equations.
New York: Dover, 1959. Six volumes, bound as three. FIRST VOLUME ONLY (parts one & two). 344pp. Thick 8vo, green cloth, d.w. New York: Dover Publications, (1959). A fine copy in a very good dust wrapper. Part I: Exact Equations and Pfaff's Problem. Part II: Ordinary Equations, Not Linear. More