APA (7th ed.) Citation

Helmler, Daniel, & Lockard. (1984). Focus on life science. Charles E. Merrill.

Chicago Style (17th ed.) Citation

Helmler, Daniel, and Lockard. Focus on Life Science. Charles E. Merrill, 1984.

MLA (8th ed.) Citation

Helmler, et al. Focus on Life Science. Charles E. Merrill, 1984.