In submitted manuscripts, any statement that is not within general knowledge should be footnoted with citation to a source for that statement. For example, citation is required for:
When citing a source, give all information as required in The Bluebook: A Uniform System of Citation (20th ed. 2015). Also, when citing works that the author expects the editors will have difficulty obtaining (for example, personal correspondence, transcribed interviews, unpublished papers), the author should send copies of the title page and all relevant pages from these sources with the manuscript.