Håkansson, H. & Carter, J.R. (1990). An interpetation of Hustedt's terms "Schattenlinie", "Perlenreihe" and "Hocker" using specimens of the Cyclotella radiosa-complex, C. distinguenda Hust., and C. cyclopuncta nov. sp. Journal of the Iowa Academy of Science, 97(4): 153-156