From: USDA Animal Welfare Act Regulations, 9 CFR Part 3 (Standards), Section 3.81 (Environment enhancement to promote psychological well-being), preamble:
“Dealers, exhibitors, and research facilities must develop, document, and follow an appropriate plan for environment enhancement adequate to promote the psychological well-being of nonhuman primates. The plan must be in accordance with the currently accepted professional standards as cited in appropriate professional journals or reference guides, and as directed by the attending veterinarian. This plan must be made available to APHIS upon request, and, in the case of research facilities, to officials of any pertinent funding agency. The plan, at a minimum, must address each of the following…”
See the source document in text or PDF format at the National Archives and Records website (home page is http://www.gpoaccess.gov/index.html). The document can also be accessed at www.iacuc.org.