The Origin and Diversification of Birds: https://www.sciencedirect.com/science/article/pii/S0960982215009458#bib4
Hummingbird snoring: https://www.youtube.com/watch?v=_uEfmQt34Nc&feature=youtu.be&fbclid=IwAR0zKDw6G0Q6_TyHKwSK0BCiTgrBbfkyLzUIXalDiLaCqWjQWQlrwzYd2mM
Evolution of the eye: https://www.youtube.com/watch?v=Zv9TFPMO6pk
