The status and challenge of dryland agriculture in developing Countries of the tropics and subtropics / 
Howard B. Sprague. 
 - Washington, DC :  US Agency for International Devel,  1981. 
 - vi, 119 p. ;  28 cm. 
<br/><br/> Open access. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Agriculture--Tropics.<br/>Tropical crops.