APA

National University Extension Association, Peterson's Guides i. & National University Extension Association. (1980). Guide to independent study through correspondence instruction. Princenton, M.J: Paterson's Guides.

Chicago

National University Extension Association, Peterson's Guides inc and National University Extension Association. 1980. Guide to independent study through correspondence instruction. Princenton, M.J: Paterson's Guides.

Harvard

National University Extension Association, Peterson's Guides i. and National University Extension Association. (1980). Guide to independent study through correspondence instruction. Princenton, M.J: Paterson's Guides.

MLA

National University Extension Association, Peterson's Guides inc and National University Extension Association. Guide to independent study through correspondence instruction. Princenton, M.J: Paterson's Guides. 1980.