1. R. Balbes and Ph. Dwinger,Coproducts of boolean algebras and chains with applications to Post algebras, Coll. Math,24 (1971), 15–25.
2. G. Grätzer,Lattice Theory, W. H. Freeman and Co., San Francisco, 1971.
3. G. Grätzer,Universal Algebra, D. Van Nostrand Co., Princeton, 1968.
4. G. Grätzer and H. Lakser,The structure of pseudo-complemented distributive lattices. III: Injectives and absolute subretracts, (to appear).
5. T.-K. Hu,Distributive extensions and quasi-framal algebras, Can. J. Math.18 (1966), 265–281.