Canadian Council on Animal Care, Olfert, E. D., Cross, B. M. et al. 1993. Guide to the Care and Use of Experimental Animals, Volume 1, 2nd Edition [Cats]. Canadian Council on Animal Care, Ottawa, Canada.

A thorough guide to the species-appropriate housing and handling of cats. The least stressful housing environment for research cats will usually be gang housing, especially if there are numerous perches [at different heights] on which individuals can rest. When establishing pairs or small groups compatibility can first be determined by observing which animals sit near each other. . ... Group pens or cages should be provided with adequate, usable, vertical space (e.g., shelves, or a tree-like structure with platforms). ... Taylor (Pers. Comm., 1990) reports long-term success with several colonies of intact males housed in groups of 6-14.