APA (7th ed.) Citation

Dryden Press. (1950). If you are writing a book (Part six). [Dryden Press].

Chicago Style (17th ed.) Citation

Dryden Press. If You Are Writing a Book (Part Six). [New York]: [Dryden Press], 1950.

MLA (9th ed.) Citation

Dryden Press. If You Are Writing a Book (Part Six). [Dryden Press], 1950.