Ehud Y. Shapiro Alternation and the Computational Complexity of Logic Programs. [Citation Graph (2, 0)][DBLP] J. Log. Program., 1984, v:1, n:1, pp:19-33 [Journal]
John C. Shepherdson Negation as Failure: A Comparison of Clark's Completed Data Base and Reiter's Closed World Assumption. [Citation Graph (5, 0)][DBLP] J. Log. Program., 1984, v:1, n:1, pp:51-79 [Journal]