Meigs, Peveril, 1953, World distribution of arid and semi-arid homoclimates: _in_ Reviews of research on arid zone hydrology: Paris, United Nations Educational, Scientific, and Cultural Organization, Arid Zone Programme-1, p. 203-209. (Classifies arid lands according to precipitation.) Nelson, R., 1988, Dryland management: the desertification problem: Environmental Department Working Paper No. 8, Washington: World Bank, 42 p. (An excellent review of the present state of knowledge concerning desertification.) Tolba, M. K., 1984, Desertification is stoppable: Arid Lands Newsletter No. 21, p. 2-9. (A discussion of the problems involved in preventing desertification and reclaiming arid lands.) Walker, A.S., 1986, Eolian geomorphology: _in_ Short, N.M., and Blair, R.W., eds., Geomorphology from space: a global overview of regional landforms: NASA SP-486, p. 447-520 (a brief review of desert processes). Warren, A. and Agnew, C., 1988, An assessment of desertification and land degradation in arid and semi-arid areas: International Institute for Environment and Development, Drylands Programme, Paper 2, London: IIED, 103 p. (An evaluation of land degradation problems.) The metric units used in this publication can be converted to English units by using the approximate conversions given below: Length 1 kilometer 0.6 of a mile 1 meter 39.37 inches 1 centimeter 0.4 inch 1 millimeter 0.04 inch Area 1 sq. kilometer 0.04 sq. mile 1 sq. meter 1.2 sq. yards 1 sq. centimeter 0.155 sq. inch Temperature To convert °Celsius to °Fahrenheit, multiply °C by 1.8 and add 32. To convert °Fahrenheit to °Celsius, subtract 32 from °F and divide the result by 1.8. [Illustration: Landsat image shows complex linear and crescentic dunes in the northeastern Taklimakan Desert of China.] _In this desert there are a great many evil spirits and also hot winds; those who encounter them perish to a man. There are neither birds above nor beasts below. Gazing on all sides as far as the eye can reach in order to mark the track, no guidance is to be obtained save from the rotting bones of dead men, which point the way._ _Explorer Fa Xian describing the Taklimakan Desert of China about 400 A.D._ This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To obtain a catalog of additional titles in the series “General Interest Publications of the U.S. Geological Survey,” write: U.S. Geological Survey Branch of Distribution P.O. Box 25286 Denver, CO 80225 ★ U. S. GOVERNMENT PRINTING OFFICE : 1992 0-332-326 QL 2