3 literature references for Bubo virginianus Stone, 1896:

Author: Dickerman, Robert W.
Year: 1991
Title: On the Validity of Bubo virginianus occidentalis Stone
Source: The Auk, vol. 108, no. 4
Author: Dickinson, Edward C., ed.
Year: 2003
Source: The Howard and Moore Complete Checklist of the Birds of the World, 3rd edition
Year: 1996
Source: database, NODC Taxonomic Code