1. Discovery of a new trilobite in the Glauconite Series of the Baltic region;Balashova;Paleontol. Z. Berlin,1961
2. Lower Palaeozoic trace fossils from eastern Newfoundland
3. Beuf S. Biju-Duval B. Charpal O. de R. ognon P. Gariel O. Bennacef A. (1971) Les Grès du Paléozoîque inférieur au Sahara (Paris), p 480.
4. Bouček B. (1973) Lower Ordovician graptolites of Bohemia (Academia, Praha), p 185.
5. Evolution and extinction rate controls;Boucot;Dev. Sedimentol,1975