Bohlen, S. R. (1998). Geology for a changing world: A science strategy for the Geologic Division of the U.S. Geological Survey, 2000-2010. U.S. G.P.O. Free on application to U.S. Geological Survey, Information Services.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Bohlen, Steven R. Geology for a Changing World: A Science Strategy for the Geologic Division of the U.S. Geological Survey, 2000-2010. Washington, Denver, CO: U.S. G.P.O. Free on application to U.S. Geological Survey, Information Services, 1998.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)Bohlen, Steven R. Geology for a Changing World: A Science Strategy for the Geologic Division of the U.S. Geological Survey, 2000-2010. U.S. G.P.O. Free on application to U.S. Geological Survey, Information Services, 1998.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.