1. Abstract and Concrete Categories;Adámek,1990
2. Connectedness and disconnectedness;Arhangelʼskiı̌;Gen. Topol. Appl.,1975
3. Splitting closure operators;Brümmer;Acta Math. Hungar.,2005
4. Interior operators in a category: Idempotency and heredity;Castellini;Topology Appl.,2011
5. Closure operators and connectedness;Castellini;Topology Appl.,1994