Not as obscure as you might think – and definitely in the public interest:
Final Incorporation by Reference Rule Implements Recommendation 2011-5 (from Legal Research Plus, with links to Fed Register)
“Today, the Office of the Federal Register (OFR) published its final rule on incorporation by reference. See Incorporation by Reference, 79 Fed. Reg. 66,267 (Nov. 7, 2014). The Freedom of Information Act allows agencies to incorporate by reference into federal regulations extrinsic materials that are “reasonably available to the class of persons affected.” 5 U.S.C. § 552(a)(1). ….