1. C. Bernardi,On the Equational Class of Diagonalizable Algebras. Studia Logica34 (1975), 321?331.
2. C.Bernardi and F.Montagna,Equivalence relations induced by extensional formulae: classification by means of a new fixed point property. To appear in Fund. Math.
3. C.Bernardi and A.Sorbi,Classifying positive equivalence relations. To appear in J. Symbolic Logic.
4. G. Boolos,The unprovability of consistency. Cambridge University Press, Cambridge, 1979.
5. R. Magari,Representation and Duality Theory for Diagonalizable Algebras. Studia Logica34 (1975), 305?313.