1. Los Yacimientos Minerales y de Hidrocarburos de Bolivia;Ahlfeld;Dep. Nac. Geol. (Bolivia), Bol.,1964
2. Distribution of the elements in our planet;Ahrens,1965
3. Bauxitic and other duricrusts on the Guiana Shield, South America;Aleva,1981
4. The iron ore deposits of Greece;Anastopoulos,1977