APA (7th ed.) Citation

Historical Records Survey (U.S.). Massachusetts, Darwin, C., Gray, A., & Loewenberg, B. J. (1973). Calendar of the letters of Charles Robert Darwin to Asa Gray. Scholarly Resources.

Chicago Style (17th ed.) Citation

Historical Records Survey (U.S.). Massachusetts, Charles Darwin, Asa Gray, and Bert James Loewenberg. Calendar of the Letters of Charles Robert Darwin to Asa Gray. Wilmington, Del.: Scholarly Resources, 1973.

MLA (8th ed.) Citation

Historical Records Survey (U.S.). Massachusetts, et al. Calendar of the Letters of Charles Robert Darwin to Asa Gray. Scholarly Resources, 1973.