Heermans, F. (1888). Two negatives make an affirmative: A photographic comedy in one act. Dramatic Pub. Co..
Chicago-referens (17:e uppl.)Heermans, Forbes. Two Negatives Make an Affirmative: A Photographic Comedy in One Act. Chicago: Dramatic Pub. Co., 1888.
MLA-referens (8:e uppl.)Heermans, Forbes. Two Negatives Make an Affirmative: A Photographic Comedy in One Act. Dramatic Pub. Co., 1888.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.