Boghossian, Paul Artin (2007): Fear of knowledge. Against relativism and constructivism. Reprint. Oxford: Clarendon Press.
Clack, Brian R. (1999): Wittgenstein, Frazer and religion. Basingstoke: Macmillan.
Clack, Brian R. (2001): “Wittgenstein and magic”. In: Robert L. and Addis Mark Arrington (Hg.): Wittgenstein and Philosophy of Religion. London: Routledge, S. 12–28.
Coliva, Annalisa (2010): “Was Wittgenstein an Epistemic Relativist?” In: Philosophical Investigations 33 (1), S. 1–23.
Kober, Michael (2007): “In the Beginning was the ‘Deed’. Wittgenstein on Knowledge and Religion”. In: Danièle Moyal-Sharrock (Hg.): Readings of Wittgenstein's On certainty. 1. Aufl. Basingstoke: Palgrave Macmillan.
Moyal-Sharrock, Danièle (2007): Understanding Wittgenstein's On certainty. Basingstoke: Palgrave Macmillan.
Moyal-Sharrock, Danièle (2013): “Knowledge and Certainty”. Forthcoming in Blackwell Companion to Wittgenstein, eds H.-J. Glock & J. Hyman.
Pritchard, Duncan (2000): “Is ‘God exists’ a ‘Hinge Proposition’ of Religious Belief?” In: International Journal for Philosophy of Religion 47, S. 129–140.
Pritchard, Duncan (2011): EPISTEMIC RELATIVISM, EPISTEMIC INCOMMENSURABILITY AND WITTGENSTEINIAN EPISTEMOLOGY’. In: Steven D. Hales (Hg.): A companion to relativism. 1. Aufl. Malden, Mass: Wiley-Blackwell (Blackwell Reference Online, 47).
Sontag, Frederick (1995): Wittgenstein and the mystical. Philosophy as an ascetic practice. Atlanta: Scholars Press (American Academy of Religion reflection and theory in the study of religion, 02).
Wittgenstein, Ludwig (1922): Tractatus Logico-Philosophicus. Translated by C.K. Ogden. Internet: http://www.gutenberg.org/ebooks/5740?msg=welcome_stranger. Access on 2014-3-15
Wittgenstein, Ludwig (1961): Notebooks 1914-1916. Edited by G.H. von Wright and G.E.M. Anscombe, translated by G.E.M. Anscombe. Oxford: Blackwell.
Wittgenstein, Ludwig (1969): On Certainty. Edited by G.E.M. Anscombe and G.H. von Wright, translated by Denis Paul and G.E.M. Anscombe. Oxford: Basil Blackwell.
Wittgenstein, Ludwig; Wright, G. H. von von; Nyman, Heikki; Pichler, Alois; Winch, Peter (2004): Culture and value. A selection from the posthumous remains. 2. Aufl. Oxford: Blackwell.
[1] Concerning the ineffability of religious credos I think that the differentiation between saying and speaking, as referenced by Moyal-Sharrock (2007: 43 f) applies. Prayers are spoken, but they cannot meaningfully be said.