APA
Gauld I D, Collins N Mark, . (1990). The biological significance and conservation of hymenoptera in Europe. Strasburg: Council of Europe.
Chicago
Gauld I D, Collins N Mark, . 1990. The biological significance and conservation of hymenoptera in Europe. Strasburg: Council of Europe.
Harvard
Gauld I D, Collins N Mark, . (1990). The biological significance and conservation of hymenoptera in Europe. Strasburg: Council of Europe.
MLA
Gauld I D, Collins N Mark, . The biological significance and conservation of hymenoptera in Europe. Strasburg: Council of Europe. 1990.