Then of course we have an article from the Ensign, the magazine of the lds church:
library.lds.org/nxt/gateway.dll/Magazines/Ensign/1987.htm/ensign%20april%201987.htm/i%20have%20a%20question.htm?fn=document-frame.htm&f=templates&2.0
I Have a Question
Questions of general gospel interest answered for guidance, not as official statements of Church policy.
Did Oliver Cowdery, one of the three special Book of Mormon witnesses, express doubt about his testimony?
Richard Lloyd Anderson, “I Have a Question,” Ensign, Apr. 1987, 23
Richard Lloyd Anderson, professor of ancient scripture, Brigham Young University. Oliver Cowdery’s strong testimony of the Book of Mormon is well documented throughout his life, and his decisive return to the Church before he died backs up his words.
In 1838 Oliver challenged the Prophet Joseph Smith’s leadership and spent the next ten years out of the Church. But in 1848 he returned to Kanesville, Iowa, the base camp of Mormon migration, and wintered in Richmond, Missouri, where his health failed. He was unable to fulfill his desire to go west with the Saints, and he died in Richmond in early 1850.
Two people who knew Oliver Cowdery best were his wife, Elizabeth Ann Whitmer, and her brother David Whitmer, also a Book of Mormon witness. David took pride in his role as the last survivor of the three witnesses, and in 1887, a year before his death, he reiterated his testimony:
“I also testify to the world, that neither Oliver Cowdery or Martin Harris ever at any time denied their testimony. … I was present at the death bed of Oliver Cowdery, and his last words were, ‘Brother David, be true to your testimony to the Book of Mormon.’ ” 1
Elizabeth first met Oliver at her house in 1829, while the Book of Mormon was being translated there. After their 1832 marriage, she was with him constantly, except for temporary separations because of Church assignments. She later reviewed his testimony:
“He always without one doubt or shadow of turning affirmed the divinity and truth of the Book of Mormon.” 2
“These plain summaries of Oliver Cowdery’s views really settle the matter, since they come from those with firsthand, intimate knowledge.
However, the importance of “the second elder” (D&C 20:3) has stimulated vicious attempts to neutralize his powerful support of the Restoration. Besides seeing an angel and the plates from which the Book of Mormon was translated, Oliver was also with Joseph Smith when John the Baptist and later Peter, James, and John restored the two priesthoods. Evidently some have wanted a Cowdery denial enough to invent two documents that contradict history.
A dozen major archives in the U.S. have a strange typescript headed “A Confession of Oliver Overstreet,” in which the above-named character claims that he was bribed to impersonate Oliver Cowdery in a return to the Church. That claim is fairly easy to dismiss, for if that were so, the whereabouts of the real Oliver Cowdery could be traced somewhere else. But some two dozen Latter-day Saints, half of them Oliver’s former close friends, detail his return in their journals and in the Church’s official minute books. Moreover, sale of Oliver’s Wisconsin property before he returned appears in recorded deeds.