Shawkey, Matthew D.; Beck, Michelle L.; Hill, Geoffrey E. Use of a gel documentation system to measure feather growth bars. J. Field Ornithol. 2003, 74 (2): 125–128. S2CID 55380093. doi:10.1648/0273-8570-74.2.125(英语).
fws.gov
Trail, Pepper. Wing Feathers(PDF) (报告). U.S. Fish and Wildlife Service. 2001 [2023-06-30]. (原始内容(PDF)存档于2017-02-06) (英语).
Shawkey, Matthew D.; Beck, Michelle L.; Hill, Geoffrey E. Use of a gel documentation system to measure feather growth bars. J. Field Ornithol. 2003, 74 (2): 125–128. S2CID 55380093. doi:10.1648/0273-8570-74.2.125(英语).