If you found your reference in an academic database (for example, Hein Online), the database URL is not included.
If you found your reference on the web (for example, in the United States, Department of State, Office of the Historian, Historical Documents) add the DOI (or, if a DOI is not available, the URL), after the final period.
See page 296 of the Publication Manual of the American Psychological Association, (2020) for more information.
FRUS is an edited collection of primary source materials (memos, letters, transcripts, etc).
The Publication Manual of the American Psychological Association does not provide specific guidance on citing the Foreign Relations of the United States. (FRUS). Putting together the citation is a matter of following basic citation rules that make it easy for your readers to go from the parenthetical reference to the entry in your Reference List. In addition, your Reference List entry should direct users to exactly where the item is within the collection.
*Note: Because FRUS volumes are published many years after the periods covered, the date published will be different than the date of the volume.
Example: A letter written by a diplomat to the Secretary of State.
Since you need to make it easy for your reader to locate the Reference from your in-text citation, you may decide to use the author of a memorandum or letter as the first element.
Alternatively, many FRUS documents are identified in the title by type of document, e.g., letter to, memorandum of, transcript of, etc. In this case, you may wish to use this word as the parenthetical reference to the first element of your Reference List entry (and referencing the individuals by name or title in the body of the text).