21.18—Tables of contents.
A table of contents shall be used at the beginning of the part whenever a new part is introduced, an existing part is completely revised, or a group of sections is revised or added and set forth as a subpart or otherwise separately grouped under a center head. The table shall follow the part heading and precede the text of the regulations in that part. It shall also list the headings for the subparts, undesignated center headings, sections in the part, and appendix headings to the part or subpart.