de Kloet, RS; de Kloet SR (2005). "The evolution in the spindlin gene in birds: Sequence Examination of an intron in the spindlin W and Z gene reveals four important divisions from the Psittaciformes". Their heads, https://imogenuojp236960.glifeblog.com/29504374/detailed-notes-on-cockatoos-parrots-for-sale