APA

Duff C., Stamford P., . (1960). German for beginners. New York - US: Barnes & noble, Inc.

Chicago

Duff Charles, Stamford Paul, . 1960. German for beginners. New York - US: Barnes & noble, Inc.

Harvard

Duff C., Stamford P., . (1960). German for beginners. New York - US: Barnes & noble, Inc.

MLA

Duff Charles, Stamford Paul, . German for beginners. New York - US: Barnes & noble, Inc. 1960.