* Herrlich, Horst & Strecker, George E.: Categorical Topology - its origins, as examplified by the unfolding of the theory of topological reflections and coreflections before 1971.
* Herrlich, Horst & Strecker, George E.: Categorical Topology — its origins, as examplified by the unfolding of the theory of topological reflections and coreflections before 1971.