S. Schmelzle, L. Helfen, R. A. Norton, and M. Heethoff, “The ptychoid defensive mechanism in Phthiracarus longulus (Acari, Oribatida, Phthiracaroidea): Exoskeletal and muscular elements”, SOIL ORG, vol. 82, no. 2, p. 253, Aug. 2010.