550 O Longwell, Chester Ray, 1887- Outlines of physical geology, by Chester R. Longwell... Adolph Knopf... Richard F. Flint... 2d. ed. New York, John Wiley & sons, Inc., 1941. ix. 381 p. ilus. (inc. mapas) 23 cm. (En Outlines of geology... New York, John Wiley & sons, Inc., 1941)