Ann. Sci. Nat. (5) xi. Zool. 1869, p. 377.
Zur Morphologie des Tracheensystems, Helsingfors, 1877, p. 38.
Zool. Anz. xiii. 1890, p. 500.
The following works convey the best information: Evans's British Libellulinae or Dragon-flies, illustrated in a series of lithographic drawings, 1845. Hagen, "A Synopsis of the British Dragon-flies," in Entomologists' Annual, 1857. M‘Lachlan, Catalogue of the British Neuroptera, published by the Entomological Society of London in 1870; and "The British Dragon-flies annotated," Entom. Month. Mag. xx. 1884, pp. 251-256.
Rev. d'Entomol. v. 1886, p. 232.