1. Adams, M. E. andW. Dziobiak, 1994, ?Q-universal quasivarieties of algebras?,Proc. Amer. Math. Soc. 120, 1053?1059.
2. Adams, M. E., W. Dziobiak, M. Gould, andJ. Schmid, [a], ?Quasivarieties of pseudocomplemented semilattices?Fund. Math., to appear.
3. Adams, M. E., V. Koubek, andJ. Sichler, 1985, ?Homomorphisms and endomorphisms of distributive lattices?Houston J. Math. 11, 129?145.
4. Birkhoff, G., 1946 (1945), ?Universal algebra? in:Proc. First. Canadian Math. Congress, Montr�al 1945 University of Toronto Press, Toronto, 310?326.
5. Burris, S. andH.P. Sankappanavar, 1981,A Course in Universal Algebra Springer-Verlag, New York.