Diversification of Ramphastinae (aves, Ramphastidae) prior to the Cretaceous/Tertiary boundary as shown by molecular clock of mtDNA sequences - Nahum, Laila Alves; Pereira, Sérgio Luiz; Fernandes, Flora Maria de Campos; Matioli, Sergio Russo; Wajntal, Anita (Genetics and Molecular Biology, 2003)