M.  Kawakatsu, Ogren, R. E., Froehlich, E. M., and Sasakil, G. Y., ?Additions and corrections of the previous land planarian indices of the world (Turbellaria, Seriata, Tricladida, Terricola)?, Bull.Fuji Women?s College, vol. 39, pp. 11-120, 2001.

R. E.  Ogren and Sluys, R., ?The genus Humbertium gen. nov., a new taxon of the land planarian family Bipaliidae (Tricladida, Terricola)?, Belg. J. Zool., vol. 131, pp. 201-204, 2001.

M.  Kawakatsu, Sluys, R., and Ogren, R. E., ?Seven new species of land planarian from Japan and China (Platyhelminthes, Tricladida, Bipaliidae), with a morphological review of all Japanese bipaliids and a biogeographic overview of Far Eastern species?, Belgian Journal of Zoology, vol. 135, pp. 53-77, 2005.