1. Allaire, E.B. 1959. Tractatus 6.3751. Analysis 19 (5): 100–105.
2. Austin, J. 1980/2000. Wittgenstein’s Solutions to the Colour Exclusion Problem. In Ludwig Wittgenstein: Critical Assessments, vol. 1, ed. S. Shanker. Abingdon: Routledge.
3. Drury, M.O.C. 1984. Conversations with Wittgenstein. In Recollections of Wittgenstein, ed. R. Rhees. Oxford: Oxford UP.
4. Friedlander, E. 2001. Signs of Sense: Reading Wittgenstein’s Tractatus. Harvard: Harvard UP.
5. Gier, N. 1981. Wittgenstein and Phenomenology: A comparative Study of the Later Wittgenstein, Husserl, Heidegger, and Merleau-Ponty. Albany: State University of NY Press.