Voegelin, E., & Franz, M. (2000). The Ecumenic Age ([New ed.].). University of Missouri Press.

Voegelin, Eric, and Michael Franz. The Ecumenic Age. [New ed.]. Columbia, Mo. ; London: University of Missouri Press, 2000.

Voegelin, Eric, and Michael Franz. The Ecumenic Age. [New ed.]. University of Missouri Press, 2000.