- Confessionalism is a term employed by historians to refer to "the creation of fixed identities and systems of beliefs for separate churches which had previously been more fluid in their self-understanding, and which had not begun by seeking separate identities for themselves—they had wanted to be truly Catholic and reformed." (MacCulloch, The Reformation: A History, p. xxiv.)
- Classification of Protestant Denominations (PDF). Pew Forum on Religion & Public Life / U.S. Religious Landscape Survey. [27 September 2009].
- Nondenominational Congregations Research at Hartford Institute for Religion Research website 互联网档案馆的存檔，存档日期2016-04-23.. Hirr.hartsem.edu. Retrieved on 2010-11-03.
- Religion. Gallup. 2012.