MPEP § 315
The Office does not process requests for "indexing" or "cross-referencing" additional patent numbers or application numbers against a document, other than an assignment, previously recorded in the Assignment Recordation Branch. Such requests do not comply with 37 CFR 3.11, 3.28, and 3.31, which require that each request for recordation include the document to be recorded and a cover sheet.
Therefore, even where a document has already been recorded in the Assignment Recordation Branch in connection with a patent or patent application, a party that wishes recordation of that document with respect to additional patents and/or patent applications must submit the following to the Assignment Recordation Branch:
The Office will assign a new recording date to that submission, update the assignment database, and include the cover sheet and document as part of the official record.