de Kloet, R. S.; de Kloet, S. R. (2005). «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». Molecular Phylogenetics and Evolution36 (3): 706–721. PMID16099384. doi:10.1016/j.ympev.2005.03.013.
de Kloet, R. S.; de Kloet, S. R. (2005). «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». Molecular Phylogenetics and Evolution36 (3): 706–721. PMID16099384. doi:10.1016/j.ympev.2005.03.013.