APA

English Languaje Services, . (1969). English grammar exercises. Canadá: Coller-McMillan.

Chicago

English Languaje Services, . 1969. English grammar exercises. Canadá: Coller-McMillan.

Harvard

English Languaje Services, . (1969). English grammar exercises. Canadá: Coller-McMillan.

MLA

English Languaje Services, . English grammar exercises. Canadá: Coller-McMillan. 1969.