De Kloet, Rolf S.; De Kloet, Siwo R. "The evolution of the spindlin gene in birds: sequence analysis of an intron of the spindlin W and Z gene reveals four major divisions of the Psittaciformes". Mol. Phylogenet. Evol. 36 (3). September 2005: 706–21. doi:10.1016/j.ympev.2005.03.013. PMID16099384.
De Kloet, Rolf S.; De Kloet, Siwo R. "The evolution of the spindlin gene in birds: sequence analysis of an intron of the spindlin W and Z gene reveals four major divisions of the Psittaciformes". Mol. Phylogenet. Evol. 36 (3). September 2005: 706–21. doi:10.1016/j.ympev.2005.03.013. PMID16099384.