Another Variant of Natural Deduction. - Irving M. Copi (J. Symb. Log., 1956)

Nineteenth Meeting of the Association for Symbolic Logic. - Irving M. Copi; R. L. Wilder (J. Symb. Log., 1956)

Realization of Events by Logical Nets. - Irving M. Copi; Calvin C. Elgot; Jesse B. Wright (J. ACM, 1958)