A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Other punctuation within numbers
Numbers
Part III. Style 20 spelling

Numbers sometimes include other internal punctuation. For periods (decimals), see 23.1.3 and 23.1.4; for colons, see 23.1.5; for hyphens, see 23.1.1 and 23.1.3; for dashes, see 23.2.4.