APA-referens (7:e uppl.)

Marcus, S. P., & Haeckel, E. (1910). What is this universe?: Christian faith versus monist dreams. Funk and Wagnalls company.

Chicago-referens (17:e uppl.)

Marcus, Sigismund Philipp, och Ernst Haeckel. What Is This Universe?: Christian Faith Versus Monist Dreams. London, New York: Funk and Wagnalls company, 1910.

MLA-referens (8:e uppl.)

Marcus, Sigismund Philipp, och Ernst Haeckel. What Is This Universe?: Christian Faith Versus Monist Dreams. Funk and Wagnalls company, 1910.