EDZ-varieties: The Schreier property and epimorphisms onto
Epics in the category of k-groups need not have dense range
Epimorphic Extensions of Non-Commutative Rings
Epimorphisms and semilattices of semigroups.
Epimorphisms of regular rings
Every topological category is convenient for Gelfand Duality.
Existence theorems for commutative diagrams.
Extremal subobjects of complete posets