1. Betchaku, T.: A copper sulfate-silver nitrate method for nerve fibres of planarians. Stain Technol. 35, 215?218 (1960).
2. Bettendorf, H.: Ueber Musculatur und Sinneszellen der Trematoden. Zool. Jb., Abt. Anat. u. Ontog. 10, 307?358 (1897).
3. Braun, M.: Vermes. In: Bronns Klass. Ord. Thierr. 4 (1890, 1892).
4. Cheng, T. C.: Further studies on the parenchymal cells of digenetic trematodes. Proc. Pennsylvania Acad. Sci. 34, 166?172 (1960).
5. ?: Studies on the morphogenesis, development and germ cell cycle in the sporocysts and cercariae of Glypthelmins pennsylvaniensis Cheng, 1961 (Trematoda: Brachycoeliidae). Proc. Pennsylvania Acad. Sci. 35, 10?22 (1961).