Smith, G. ., Brenowitz, E. ., Beecher, M. ., & Wingfield, J. . (1997). Seasonal changes in testosterone, neural attributes of song control nuclei, and song structure in wild songbirds. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 17(15), 6001-10. Retrieved from http://www.jneurosci.org/cgi/pmidlookup?view=long&pmid=9221796 (Original work published 1997)

Smith, G. ., Brenowitz, E. ., & Wingfield, J. . (1997). Seasonal changes in the size of the avian song control nucleus HVC defined by multiple histological markers. The Journal of Comparative Neurology, 381(3), 253-61. https://doi.org/10.1002/(sici)1096-9861(19970512)381:3<253::aid-cne1>3.0.co;2-1 (Original work published 1997)

Smith, G. ., Brenowitz, E. ., & Wingfield, J. . (1997). Roles of photoperiod and testosterone in seasonal plasticity of the avian song control system. Journal of Neurobiology, 32(4), 426-42. https://doi.org/10.1002/(sici)1097-4695(199704)32:4<426::aid-neu6>3.0.co;2-8

Smith, G. ., Brenowitz, E. ., Wingfield, J. ., & Baptista, L. . (1995). Seasonal changes in song nuclei and song behavior in Gambel’s white-crowned sparrows. Journal of Neurobiology, 28(1), 114-25. https://doi.org/10.1002/neu.480280110