Lessenberry, D. D. (1942). 20th century typewriting (4th ed.). South-western Pub. Co..
Chicago-referens (17:e uppl.)Lessenberry, D. D. 20th Century Typewriting. 4th ed. Cincinnati : New York [etc.]: South-western Pub. Co., 1942.
MLA-referens (8:e uppl.)Lessenberry, D. D. 20th Century Typewriting. 4th ed. South-western Pub. Co., 1942.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.