Climate aridity index (Budyko-Ratio) / 
Henning, D.
Flohn, H.
United Nations.Conference on desertification.
Nairobi :  U.N. Environmental Project, 
1977.
Explanatory note prepared by FAO, Unesco and WMO.
U.N. conference on desertification, 29 Aug-9 Sep 1977. (A/CONF. 74/31).