Stevens, A. 1990. Gorilla husbandry/enrichment at the Dallas Zoo. Proceedings: Columbus Zoo Gorilla Workshop, A-5 (Abstract).

Unintrusive husbandry techniques during cleaning and feeding, such as shifting animals, allow keepers to easily incorporate environmental enrichment components during their normal routine. To create a stimulating and diverse environment, keepers supply simple, economic [unspecified] items which allow the gorillas to modify their immediate surroundings, and exhibit more of their natural behavior.