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In 1946 Emil Leon Post (Bulletin of Amer. Math. Soc. 52 (1946), 264 - 268)defined a famous correspondence decision problem which is nowadays called thePost Correspondence Problem, and he proved that the problem is undecidable. Inthis article we follow the steps of Post, and give another, simpler and morestraightforward proof of the undecidability of the problem using the samesource of reduction as Post original did, namely, the Post Normal Systems.

Another proof of undecidability for the correspondence decision problem - Had I been Emil Post