Minimal Boolean expressions with more than two levels of sums and products

This paper presents a new approach to the problem of multi-level Boolean minimization. Conventional two-level minimization methods are embedded in a process that makes extensive use of the properties of incompletely specified functions. Particular attention is given to the problem of obtaining minimal sums-of-products-of-sums. Then the approach is extended to minimal expressions with more than three levels and to "absolute" minimal expressions. Several examples are worked out.