The MHRA Style Guide Online
A Handbook for Authors and Editors • Third Edition
From Chapter 10, 'Footnotes and Endnotes'
The term ‘notes’ as used in this chapter applies equally to footnotes and to endnotes (i.e. references printed at the end of an article, chapter, or book).
Notes are an interruption to the reader and should be kept down to what is strictly necessary. They are intended primarily for documentation and for the citation of sources relevant to the text. They should not be used to provide additional bibliographical material on the general subject being treated, but which is not directly needed. Nor should they normally include extra expository material. Such material, if apposite and useful, is often better incorporated into the text or added as an appendix. Only after the most careful consideration should it be included in a note.
All notes, whether or not they form complete sentences, should end with full stops.