Harnack, A. (1957). What is Christianity? Harper & Brothers.
芝加哥风格引文Harnack, Adolf. What Is Christianity? New York: Harper & Brothers, 1957.
MLA引文Harnack, Adolf. What Is Christianity? Harper & Brothers, 1957.
警告：这些引文格式不一定是100％准确.
APA引文