Thielcke, G. Vogelwarte Radolfzell, Radolfzell, Max Planck Institut für Ornithologie, Max Planck Society;
Thielcke, G. (1986). Constant proportions of mixed singers in tree creeper populations (Certhia-familiaris). Ethology, 72(2), 154-164. doi:10.1111/j.1439-0310.1986.tb00615.x.