An oral history interview, personal paper, unpublished letter, or organizational record of a nongovernmental entity that was not created or maintained in the conduct of official business of a governmental body and that is held by a private or public archival and manuscript repository for the purpose of historical research is excepted from the requirements of § 552.021 to the extent that the archival and manuscript repository and the donor of the interview, paper, letter, or record agree to limit disclosure of the item.