Harnack, A. (1957). What is Christianity? Harper & Brothers.
Chicago-čujuhus (17. p.)Harnack, Adolf. What Is Christianity? New York: Harper & Brothers, 1957.
MLA-čujuhus (9. p.)Harnack, Adolf. What Is Christianity? Harper & Brothers, 1957.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.