Flachs, K. 1931 . [Diseases and parasites of ornamental plants: Identification and reference book for biologists, plant pathologists and gardeners]. Verlagsbuchhandlung von Eugen Ulmer Stuttgart, Germany 558 pp.

Notes: Year 1931 doesn't appear on paper, but is in brackets in National Agriculture Library cataloging; title in German: Krankheiten und Parasiten der Zierpflanzen: Ein Bestimmungs- und Nachschlagebuch für Biologen, Pflanzenärzte, Gärtner und Gartenfreunde. Scale species mentioned include Chrysomphalus dictyospermi, Aspidiotus hederae, Eriococcus spurius, E. aceris, Phenacoccus aceris, Lachnus longirostris, Pseudococcus adonidum, P. citri, P. hibernicus, Eriococcus uvae-ursi, E. coccineus, E. ericae, E. spurius, Lepidosaphes ulmi, Chionaspis salicis, Orthezia urticae, Eulecanium corni, E. coryli, Fonscolombea fraxini and Phenacoccus aceris.