Wittgenstein, L. (1971). Prototractatus: An early version of Tractatus logico-philosophicus. Routledge & Kegan Paul.
Lua i Stíl Chicago (17ú heag.)Wittgenstein, Ludwig. Prototractatus: An Early Version of Tractatus Logico-philosophicus. London: Routledge & Kegan Paul, 1971.
Lua MLA (9ú heag.)Wittgenstein, Ludwig. Prototractatus: An Early Version of Tractatus Logico-philosophicus. Routledge & Kegan Paul, 1971.
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