At the suggestion of Alonzo Church, Emil Post in a paper published in 1947, first proved "a certain Problem of Thue" to be unsolvable, what Martin Davis states as "...the first unsolvability proof for a problem from classical mathematics -- in this case the word problem for semigroups."
Na prijedlog Alonza Churcha, Emil Post je u radu objavljenom 1947. prvi dokazao nerješivost "određenog problema Thuea", što Martin Davis iskazuje kao "...prvi dokaz nerješivosti za problem klasične matematike - u ovom slučaju problem riječi za polugrupe."