1 CFR 21.21 - General requirements: References.
(a) Each reference to the Code of Federal Regulations shall be in terms of the specific titles, chapters, parts, sections, and paragraphs involved. Ambiguous references such as “herein”, “above”, “below”, and similar expressions may not be used.
(b) Each document that contains a reference to material published in the Code shall include the Code citation as a part of the reference.
(c) Each agency shall publish its own regulations in full text. Cross-references to the regulations of another agency may not be used as a substitute for publication in full text, unless the Office of the Federal Register finds that the regulation meets any of the following exceptions:
(1) The reference is required by court order, statute, Executive order or reorganization plan.
(2) The reference is to regulations promulgated by an agency with the exclusive legal authority to regulate in a subject matter area, but the referencing agency needs to apply those regulations in its own programs.
(3) The reference is informational or improves clarity rather than being regulatory.
(4) The reference is to test methods or consensus standards produced by a Federal agency that have replaced or preempted private or voluntary test methods or consensus standards in a subject matter area.
(5) The reference is to the Department level from a subagency.