Melo, Martim; O'ryan, Colleen (2007). "Genetic differentiation between Príncipe Island and mainland populations of the grey parrot (Psittacus erithacus), and implications for conservation". Molecular Ecology. 16 (8): 1673–1685. Bibcode:2007MolEc..16.1673M. doi:10.1111/j.1365-294X.2006.03128.x. PMID17402982.
Lopes, Daniel da Costa; Martin, Rowan O.; Indjai, Bucar; Monteiro, Hamilton; Henriques, Mohamed; Regalla, Aissa; Catry, Paulo (2018). "Food diversity of Timneh Parrots (Psittacus timneh ) in the Bijagós archipelago, Guinea-Bissau". African Journal of Ecology. 56 (4): 1039–1043. Bibcode:2018AfJEc..56.1039L. doi:10.1111/aje.12544.
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Melo, Martim; O'ryan, Colleen (2007). "Genetic differentiation between Príncipe Island and mainland populations of the grey parrot (Psittacus erithacus), and implications for conservation". Molecular Ecology. 16 (8): 1673–1685. Bibcode:2007MolEc..16.1673M. doi:10.1111/j.1365-294X.2006.03128.x. PMID17402982.
Lopes, Daniel da Costa; Martin, Rowan O.; Indjai, Bucar; Monteiro, Hamilton; Henriques, Mohamed; Regalla, Aissa; Catry, Paulo (2018). "Food diversity of Timneh Parrots (Psittacus timneh ) in the Bijagós archipelago, Guinea-Bissau". African Journal of Ecology. 56 (4): 1039–1043. Bibcode:2018AfJEc..56.1039L. doi:10.1111/aje.12544.
Melo, Martim; O'ryan, Colleen (2007). "Genetic differentiation between Príncipe Island and mainland populations of the grey parrot (Psittacus erithacus), and implications for conservation". Molecular Ecology. 16 (8): 1673–1685. Bibcode:2007MolEc..16.1673M. doi:10.1111/j.1365-294X.2006.03128.x. PMID17402982.