In dates: 1897-8, not 1897-98 (use en rules); and from 1672 to 1674, not from 1672-74.
Print: 250 B.C.; but when it is necessary to insert A.D. the letters should precede the year, as A.D. 250. In B.C. references, however, always put the full date, in a group of years, e.g. 185-122 B.C.
When preliminary pages are referred to by lower-case roman numerals, no full points should be used after the numerals. Print:
p. ii, pp. iii-x; not p. ii., pp. iii.-x.
When references are made to two successive text-pages print pp. 6, 7, if the subject is disconnected in the two pages. But if the subject is continuous from one page to the other, then print pp. 6-7. The compositor in this must be guided by his copy. Print p. 51 sq. if the reference is to p. 51 and following page; but pp. 51 sqq. when the reference is to more than a single page following.[74]
In a sequence of figures use an en rule, as in the above examples; but in such cases as Chapters III—VIII use an em rule.
Begin numbered paragraphs: 1. 2. &c.; and clauses in paragraphs: (1) (2) (3), &c. If Greek or roman lower-case letters are written, the compositor must follow copy. Roman numerals (I. II. III.) are usually reserved for chapters or important sections.
References in the text to footnotes should be made by superior figures—which are to be placed, as regards punctuation marks, according to the sense. If a single word, say, is extracted and referred to, the reference must be placed immediately after the word extracted and before the punctuation mark. But if an extract be made which includes a complete sentence or paragraph, then the reference mark must be placed outside the last punctuation mark. Asterisks, superior letters, &c., may be used in special cases. Asterisks and the other signs (* † ‡ &c.) should be used in mathematical works, to avoid confusion with the workings.
In Mathematics, the inferior in P1′ should come immediately after the capital letter.