Lee, Patricia L. M.; Clayton, Dale H.; Griffiths, Richard; Page, Roderic D. M. (9-07-1996). "Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome b mitochondrial DNA sequences". Proceedings of the National Academy of Sciences of the United States of America93 (14): 7091–7096. ISSN0027-8424. doi:10.1073/pnas.93.14.7091.
Lee, Patricia L. M.; Clayton, Dale H.; Griffiths, Richard; Page, Roderic D. M. (9-07-1996). "Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome b mitochondrial DNA sequences". Proceedings of the National Academy of Sciences of the United States of America93 (14): 7091–7096. ISSN0027-8424. doi:10.1073/pnas.93.14.7091.