Kriesell, H. J., Le Bohec, C., Cerwenka, A. F., Hertel, M., Robin, J.-P., Ruthensteiner, B., et al. (2020). Vocal tract anatomy of king penguins: Morphological traits of two-voiced sound production. Frontiers in Zoology, 17: 5. doi:10.1186/s12983-020-0351-8.