Darwin, C. (1939). Calendar of the Letters of Charles Robert Darwin to Asa Gray. The Historical Records Survey.
芝加哥风格引文Darwin, Charles. Calendar of the Letters of Charles Robert Darwin to Asa Gray. Boston, Mass.: The Historical Records Survey, 1939.
MLA引文Darwin, Charles. Calendar of the Letters of Charles Robert Darwin to Asa Gray. The Historical Records Survey, 1939.
警告：这些引文格式不一定是100％准确.