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.
Lua i Stíl Chicago (17ú heag.)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.
Lua MLA (9ú heag.)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.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.