Loseva, E.I. (1980). Novye dannye o strukture pantsiria dvukh predstavitelei roda Cyclotella iz verkhnepliotsenovykh otlozheniia basseina r. kamy. [Some new data on the frustule of two representatives of the genus Cyclotella from upper Pliocene deposits in Kama River Basin]. Botanicheskii Zhurnal, 65(11): 1618-1622