1. Abstract and Concrete Categories;Adámek,1990
2. B. Banaschewski, A Sobering Suggestion, Seminar Notes, Cape Town, 1999
3. Stone Spaces;Johnstone,1982
4. Approach spaces: a common supercategory of TOP and MET;Lowen;Math. Nachr.,1989
5. Approach Spaces: the Missing Link in the Topology-Uniformity-Metric Triad;Lowen,1997