We need to clarify some definitions. What does it mean to minimize a function "in the basis of CNF": to give the shortest formula using the connectives from CNF, or to give the shortest CNF? What does it mean to show the minimum function "in the

*bases*"? What is "Schaeffer Pierce"? Do you mean to express the function using Sheffer stroke and Peirce arrow?

A usual way to minimize functions is using a Karnaugh map. Apparently, Quine–McCluskey algorithm is functionally identical to Karnaugh mapping (

Wikipedia). Another possibility is that there are two shortest CNFs (or DNFs) with the same number of connectives (or literals). Finally, maybe the two ways refers to the way you show the equivalence of the original and the minimum function: using truth tables and the laws of Boolean algebra.