Gamuts and cofibrations R. Rosebrugh, R. J. Wood (1990) Cahiers de Topologie et Géométrie Différentielle Catégoriques
Generating families in a topos. Kenney, Toby (2006) Theory and Applications of Categories [electronic only]
Glueing analysis for complemented subtoposes. Kock, Anders, Plewe, Till (1996) Theory and Applications of Categories [electronic only]