I.: Bent, Arthur : Life Histories of North American Nuthatches, Wrens, Thrashers and their Allies. New York, Dover Pub. 1964. Pbk. ISBN 048621088X / II.: Robbins, Chandler ; Bruun, Bertel: A Guide to Field Identification. Birds of North America. New York, Golden Press 1966. Hardback. / III.: Griscom, Ludlow (Ed.): Audubon’s Birds of America. New York, Macmillan 1950. Hardback. / IV.: Peterson, Roger : A Field Guide to the Birds of Texas and Adjacent States. (= Peterson Field Guide Series). Boston, Houghton Mifflin 1967. cloth. / V.: Peterson, Roger : A Field Guide to the Birds. A completely new Guide to all the Birds of Eastern and Central North Amerika (= Peterson Field Guide Series). Boston, Houghton Mifflin 1980. Pbk. ISBN 039526619X. Books with slight signs of ageing