Issue No. 04 - April (1971 vol. 20)
Paull and Unger  were the first to develop methods for solving the problem of minimizing the number of internal states of incompletely specified sequential machines. Grasselli and Luccio  improved upon these methods by introducing rules for reducing the size of the problem and by transforming the problem into a linear integer programming problem. House and Stevens  have provided a means of further reducing the size of the problem by developing an additional rule.
Covering and closure tables, incompletely specified sequential machines, minimization of internal states, reduction algorithm, reduction rules.
H.A. Curtis, "The Further Reduction of CC-Tables", IEEE Transactions on Computers, vol. 20, no. , pp. 454-456, April 1971, doi:10.1109/T-C.1971.223264