Reference

Jochen Martens, Siegfried Eck, Martin Päckert, Yue-Hua Sun (2003): Methods of Systematic and Taxonomic Research on Passerine Birds: the Timely Example of the Seicercus burkii Complex (Sylviidae) – Bonn zoological Bulletin - früher Bonner Zoologische Beiträge. – 51: 109 - 118.