Hopfen, Hans Joachim. Farm implements for arid and tropical regions, prepared by H. J. Hopfen. - Rev. ed. - Rome, Food and Agriculture Organization of the United Nations, 1976. - xii, 159 p. : illus., 23 cm. - FAO agricultural development paper ; no. 91 . Bibliography: p. [147]-150. LCCN: 73586274 Subjects--Topical Terms: Agricultural implements. LC Class. No.: S401.U6 / A13 no. 91 Dewey Class. No.: 630 / FOF 1976