Enemar, Anders, and Kerstin Wiklander. “Density and Fluctuations of a Nest-Pocket Breeding Population of the Treecreeper Certhia Familiaris over a 28-Year Period”. Ornis Svecica, vol. 24, no. 1–2, Jan. 2014, pp. 27–34, doi:10.34080/os.v24.22562.