Great grey owl (English Wikipedia)

Bull, E.L.; Duncan, J.R. (1993). "Great Gray Owl (Strix nebulosa)". In Poole, A. (ed.). The Birds of North America (online ed.). No. 041, introduction. doi:10.2173/bow.grgowl.01. S2CID 216190368. Retrieved 25 February 2017.

cites.org

"Strix nebulosa". IUCN Red List of Threatened Species. 2021. BirdLife International. 2021. doi:10.2305/IUCN.UK.2021-3.RLTS.T22689118A199144259.en. Retrieved 24 February 2022.
Hull, Joshua M.; Englis, Andrew Jr.; Medley, Joseph R.; Jepsen, Eric P.; Duncan, James R.; Ernest, Holly B.; Keane, John J. (2014). "A New Subspecies of Great Gray Owl (Strix nebulosa) in the Sierra Nevada of California, U.S.A." Journal of Raptor Research. 48 (1): 68–77. doi:10.3356/JRR-13-35.1. S2CID 84375832.
Bull, E.L.; Duncan, J.R. (1993). "Great Gray Owl (Strix nebulosa)". In Poole, A. (ed.). The Birds of North America (online ed.). No. 041, introduction. doi:10.2173/bow.grgowl.01. S2CID 216190368. Retrieved 25 February 2017.

Hull, Joshua M.; Englis, Andrew Jr.; Medley, Joseph R.; Jepsen, Eric P.; Duncan, James R.; Ernest, Holly B.; Keane, John J. (2014). "A New Subspecies of Great Gray Owl (Strix nebulosa) in the Sierra Nevada of California, U.S.A." Journal of Raptor Research. 48 (1): 68–77. doi:10.3356/JRR-13-35.1. S2CID 84375832.
Bull, E.L.; Duncan, J.R. (1993). "Great Gray Owl (Strix nebulosa)". In Poole, A. (ed.). The Birds of North America (online ed.). No. 041, introduction. doi:10.2173/bow.grgowl.01. S2CID 216190368. Retrieved 25 February 2017.

Hull, Joshua M.; Englis, Andrew Jr.; Medley, Joseph R.; Jepsen, Eric P.; Duncan, James R.; Ernest, Holly B.; Keane, John J. (2014). "A New Subspecies of Great Gray Owl (Strix nebulosa) in the Sierra Nevada of California, U.S.A." Journal of Raptor Research. 48 (1): 68–77. doi:10.3356/JRR-13-35.1. S2CID 84375832.