I looked at other online sources, and the one I found says that he is a member of the church of Jesus Christ of latter-day saints, which are informally mormons.
Neal Neff has written: 'Neal Neff's New National Poems' -- subject(s): Poetry, History
E. Neff has written: 'Carlyle' 'Edward Arlington Robinson'
Karl Neff has written: 'Die Gedichte des Paulus Diaconus'
Michael Paul Neff has written: 'Aesthetic exploration and refinement'
W. F. Neff has written: 'Victorian working women'
Henry Asbury Christian has written: 'The Oxford medicine' -- subject(s): Medicine, Practice
Hans Neff has written: 'Physikalische Messtechnik' -- subject(s): Physical measurements
Henry A. Stimson has written: 'The place of Christian education in the civilization of the West' -- subject(s): Christian education
Henry William Steiger has written: 'Christian Science and philosophy' -- subject(s): Christian Science
Cornelius Neff has written: 'Neal Neff's New national poems' -- subject(s): History, Poetry, United States Civil War, 1861-1865
Elaine Nielsen Neff has written: 'The Wights' -- subject(s): Genealogy, Mormons 'The Nielsens'
I don't know the exact date but it was in 1973, sorry