Wilfried Schönborn, Th. Peschke (1988): Biometric Studies on Species, Races, Ecophenotypes and Individual Variations of Soil-inhabiting Testacea (Protozoa, Rhizopoda), Including Trigonopyxis minuta n. sp. and Corythion asperulum n. sp. – Archiv für Protistenkunde – 136_1988: 345 - 363.