ISBN 0-87338-838-0. Newsholme, C. (1992). Willows: The Genus Salix. ISBN 0-88192-565-9. Trybush, Sviatlana; Jahodová, Šárka; Macalpine, William; Karp, Angela...
Willow catkin Newsholme, C. (1992). Willows: The Genus Salix. ISBN 0-88192-565-9 Warren-Wren, S.C. (1992). The Complete Book of Willows. ISBN 0-498-01262-X