Physical description for original version: vi, 51 p. : 28 cm
書誌注記
Includes bibliographical references (p. 32-35)
原資料等に関する注記
原資料の出版事項: [Reston, Va.?] ; Denver, CO : Dept. of the Interior, U.S. Geological Survey : Free on application to the Books and Open-File Reports Section, 1990