1. B. Banaschewski,Injectivity and essential extensions in equational classes of algebras, inProceedings of the Conference on Universal Algebra, October 1969 (Queen’s University, Kingston, 1970) pp. 131–147.
2. B. Banaschewski and E. Nelson,Equational compactness in equational classes of algebras (preprint).
3. Bjarni Jónsson,Extensions of relational structures, inThe Theory of Models (North-Holland, Amsterdam, 1965), pp. 146–157.
4. Walter Taylor,Residually small varieties (to appear).