Chugaeva 1964. [Trilobites of the Early and Middle Ordovician of the North-East of the USSR, and Analysis of trilobites]. Comparative biostratigraphy of the Ordovician deposits of the north-east of the USSR., M. N. Chugaeva, Kh. S. Rozman & V. A. Ivanova, Comparative biostratigraphy of the Ordovician deposits of the north-east of the USSR. Trud. geol. Inst. Aka d. Nauk SSSR 106 1964: 24-85 pls. i-vi text-figs 4-22 tables 2-3 [Russian]", 1964: 24-85. Chapter pagination: 24-85