Delannay, Xavier «Evolution of male sterility mechanisms in gynodioecious and dioecious species of Cirsium (Cynareae, Compositae)». Plant Systematics and Evolution, 132, 4, 1979, p. 327. DOI: 10.1007/BF00982395.
Kiesselbach, T.A.. The structure and reproduction of corn. Cold Spring Harbor, N.Y: Cold Spring Harbor Laboratory Press, 1999, p. 3. ISBN 9780879695569. OCLC245875754.
Waldbauer, Gilbert. What good are bugs? : insects in the web of life. Cambridge, Mass.: Harvard University Press, 2003, p. 33–34. ISBN 9780674010277. OCLC50198798.