1. Toman Sikorski: “Boolean Algebras”. Springer -.Verlag, Berlin, Göttingen, Heidelberg (1960).
2. W. V. Quine: 1. Quine: 1. “The Problem of Simplifying Truth _Functions”. American math.monthly,Bd.59,(1952). 2. “A Way to Simplify Truth Functions”. American math.monthly, Bd. 62, (1957).
3. R.H. Urbano and R.K. Mueller: “A Topological Method for the Determination of the Minimal Forms of a Boolean Function”. IRE Trans.EC, September 1956.
4. E.J. Mc Clúskey, jr.: “Minimization of Boolean Functions”. B.S.T.J,Bd. 35, 1956.
5. J.P. Roth: “Algebraic Topological Methods: for the Synthesis of Switching Systems III. Minimization of Nonsingular Boolean Trees”. IBM-Journal, Oktober 1959.