1. Adams, F. D. 1938.THE BIRTH AND DEVELOPMENT OF THE GEOLOGICAL SCIENCES, 506New York: Dover.
2. Ahlfeld, F. 1958.Zinn und Wolfram [TIN AND TUNGSTEN]212Stuttgart
3. Natl. Geo. Soc. Contr. Tech. Papers 1 (2);Allen E. T.,1923
4. . Am. Inst. Min. Met. Eng. SYMPOSIUM ON: ORE DEPOSITS OF THE WESTERN STATES. pp.797New York