1. Fibred categories and the foundation of naive category theory;Bénabou;J. Symbolic Logic,1985
2. Fibred and cofibred categories;Gray,1966
3. Formal Category Theory: Adjointness for 2-Categories;Gray,1974
4. Fibrations, logical predicates and related topics;Hermida,1993
5. Technical Report ECS-LFCS-93-277, also available as Aarhus Univ. DAIMI Technical Report PB-462.