The Cambro-Ordovician Formations and Faunas of South Korea. Part X. Stratigraphy of the Chosen Group in Korea and South Manchuria and its relation to the Cambro-Ordovician Formations of other areas. Section B. The Chosen Group of North Korea and north east China. Journal of the Faculty of Science Tokyo University Sect II, 16(2) 1966: 209-311. [Zoological Record Volume 103]