APA

Ojakangas R. W., . (1991). Schaum's outline of theory and problems of introductory geology. New York: McGraw-Hill Pub. Co.

Chicago

Ojakangas Richard W, . 1991. Schaum's outline of theory and problems of introductory geology. New York: McGraw-Hill Pub. Co.

Harvard

Ojakangas R. W., . (1991). Schaum's outline of theory and problems of introductory geology. New York: McGraw-Hill Pub. Co.

MLA

Ojakangas Richard W, . Schaum's outline of theory and problems of introductory geology. New York: McGraw-Hill Pub. Co. 1991.