Boyd K. Packer teaches that only the Standard Works and statements written under the assignment of the First Presidency and Quorum of the Twelve are to be considered official Church declarations.
Boyd K. Packer, "The law and the Light," in Jacob Through the Words of Mormon: To Learn with Joy, ed. Monte S. Nyman and Charles D. Tate, Jr. (Provo, UT: Brigham Young University, 1990), 1
Only the Standard Works and statements written under assignment of the First Presidency and the Council of the Twelve Apostles are considered official declarations by The Church of Jesus Christ of Latter-day Saints. The talk which follows was given without such assignment and no such approval has been sought or given. The author alone is responsible for the views set forth therein. They do not necessarily represent the Church.