The MHRA Style Guide Online
A Handbook for Authors and Editors • Third Edition
From Chapter 10, 'Footnotes and Endnotes'
10.2 Methods of Limiting Notes
Simple references (such as line numbers or page references to a book already cited in full) can usually be incorporated in the text, normally in parentheses after quotations. A string of note references to the same text can be avoided by stating after the first full note citation: ‘Further references [to this edition, etc.] are given after quotations in the text.’ (See also 11.3.)
The number of notes can often be kept down by grouping together, in one note, references to several sources mentioned close together in the same paragraph. In particular, adjacent references to several pages of the same publication should be cited together in a single note. No note, however, should document references for more than one paragraph.
Notes should not repeat information already clear from the text: if, for example, the author has been named before a quotation there is no need to repeat the name in a note reference. If there is a bibliography to a book or article, notes can also be reduced.