Thielcke, Gerhard Vogelwarte Radolfzell, Radolfzell, Max Planck Institut für Ornithologie, Max Planck Society;
Thielcke, G. (1966). Ritualized distinctiveness of song in closely related sympatric species. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 251(772), 493-497. doi:10.1098/rstb.1966.0041.