Waldohreule [online]. AG Eulen – Arbeitsgemeinschaft zum Schutz bedrohter Eulen [cit. 2010-02-19]. Dostupné online. (německy)
bto.org
blx1.bto.org
Long-eared Owl Asio otus [Linnaeus, 1758] [online]. British Trust for Ornithology [cit. 2010-02-18]. Dostupné online. (anglicky)
euring.org
European Longevity Records [online]. European Union for Bird Ringing [cit. 2009-11-17]. Dostupné online. (anglicky)
iucnredlist.org
apiv3.iucnredlist.org
The IUCN Red List of Threatened Species 2021.3. 9. prosince 2021. Dostupné online. [cit. 2021-12-27].
iucnredlist.org
Asio otus [online]. The IUCN Red List of Threatened Species [cit. 2010-02-18]. Dostupné online. (anglicky)
lynxeds.com
ibc.lynxeds.com
Long-eared Owl (Asio otus) [online]. The Internet Bird Collection (IBC) [cit. 2010-02-17]. Dostupné online. (anglicky)
nih.gov
ncbi.nlm.nih.gov
SUN, Yi, Fei Ma, Bing Xiao, Junjie Zheng, Xiaodong Yuan, Minqian Tang, Li Wang, Yefei Yu, Qingwei Li. The complete mitochondrial genomes sequences of Asio flammeus and Asio otus and comparative analysis. Science in China. Series C, Life Sciences / Chinese Academy of Sciences. 2004-12, roč. 47, čís. 6, s. 510–520. Dostupné online. ISSN1006-9305.
KIRSCHBAUM, Kari; IVORY, Alicia. Asio otus long-eared owl [online]. University of Michigan Museum of Zoology [cit. 2010-02-18]. Dostupné online. (anglicky)
uni-heidelberg.de
WINK, Michael; SAUER-GURTH, Hedi; FUCHS, Marc. Phylogenetic relationships in owls based on nucleotide sequences of mitochondrial and nuclear marker genes [online]. Chancellor, R.D. & B-U. Meyburg, Raptors Worldwide, WWGBP/MME, 2004. Dostupné online.
web.archive.org
Long–eared Owl [online]. The Cornell Lab of Ornithology [cit. 2010-02-19]. Dostupné v archivu pořízeném dne 2011-10-13. (anglicky)
BÁRTOVÁ, Eva. Kalous ušatý [online]. PtačíSvět.cz [cit. 2010-02-18]. Dostupné v archivu pořízeném dne 2008-04-08.
worldcat.org
SUN, Yi, Fei Ma, Bing Xiao, Junjie Zheng, Xiaodong Yuan, Minqian Tang, Li Wang, Yefei Yu, Qingwei Li. The complete mitochondrial genomes sequences of Asio flammeus and Asio otus and comparative analysis. Science in China. Series C, Life Sciences / Chinese Academy of Sciences. 2004-12, roč. 47, čís. 6, s. 510–520. Dostupné online. ISSN1006-9305.