Use footnotes for your in-text citations. Place the number for the footnote after the period at the end of the sentence that the reference refers to. Place the full references at the bottom of the page. The full reference will vary, depending on if the letter has been published. Only the first line of each footnote is indented. The formatting for citations are the same for footnote citations as they are for bibliographical citations. Here are two examples, one for published letters and one for unpublished letters:
[7] John Smith, Jane Smith, "The Front Lines," Letter from a Soldier to His Wife, 7 May 1943, in Voices of Soldiers: World War II, Adam Stone, ed., 1943 Volume: Year Five (New York, World War Publications, 1963), 234.
[14] John Smith, letter to Jane Smith, May 7, 1943.
Write the bibliographical citation with the following information if the letter has been published: author, addressee, document title, date written, publication title, editor's name, volume, city, publisher, date of publication, and page number. Be sure to use quotations around the document title, italicize the publication title, and put parentheses around the city, publisher, and date). Here is an example:
John Smith, Jane Smith, "The Front Lines," Letter From a Soldier to His Wife, 7 May 1943, in Voices of Soldiers: World War II, Adam Stone, ed., 1943 Volume: Year Five (New York, World War Publications, 1963), 234.
Write the bibliographical citation with the following information if the letter has not been published: author, type of communication, addressee, date. Here is an example:
John Smith, letter to Jane Smith, May 7, 1943.