Identification for ringers. 3, The genus Sylvia /
by Kenneth Williamson.
- 2nd ed., revised and enlarged.
- Tring : British Trust for Ornithology, 1968.
- 75 p., plates : ill. ; 22 cm.
- British Trust for Ornithology identification guide ; no. 3 Field guide ; no. 9 .
- British Trust for Ornithology identification guide ; no. 3 Field guide (British Trust for Ornithology) ; no. 9. .