North Dakota. Department of Public Instruction. (1963). A course of study and a guide for teachers of eight grade earth science (prelim ed.). Department of Public Instruction.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)North Dakota. Department of Public Instruction. A Course of Study and a Guide for Teachers of Eight Grade Earth Science. prelim ed. Bismarck: Department of Public Instruction, 1963.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)North Dakota. Department of Public Instruction. A Course of Study and a Guide for Teachers of Eight Grade Earth Science. prelim ed. Department of Public Instruction, 1963.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.