Paul Lorenzen Algebraische und Logistische Untersuchungen Uber Freie Verbande. [Citation Graph (0, 0)][DBLP] J. Symb. Log., 1951, v:16, n:2, pp:81-106 [Journal]
Andrzej Mostowski On the Rules of Proof in the Pure Functional Calculus of the First Order. [Citation Graph (0, 0)][DBLP] J. Symb. Log., 1951, v:16, n:2, pp:107-111 [Journal]
Soren Hallden On the Semantic Non-Completeness of Certain Lewis Calculi. [Citation Graph (0, 0)][DBLP] J. Symb. Log., 1951, v:16, n:2, pp:127-129 [Journal]