Reference
Günther Pass, Monika Merl, Barbara-Amina Gereben-Krenn, Nikolaus U. Szucsich, Markus Tögel, John Plant (2006): Phylogenetic Relationships of the Orders of Hexapoda: Contributions from the Circulatory Organs for a Morphological Data Matrix – Arthropod Systematics and Phylogeny – 64: 165 - 203.