1. THE STRATIGRAPHY OF THE MAWDDACH GROUP IN THE CAMBRIAN SUCCESSION OF NORTH WALES
2. Amos, A. J., Camacho, H. H., Castellaro, H. A. and Menendez, C. A. 1963.Guia paleontologia Argentina. Parte 1: Paleozoico. Seccion I‐Cambricas; Seccion II‐Ordovicicas, 165Buenos Aires: Consejo nacional de investigaciones cientifica y tecnicas.
3. Anonymous. 1990.Sinian to Permian stratigraphy and palaeontology of the Tarim Basin, Xinjiang. (I). Kuruktag region. Southern Xinjiang Petroleum Prospecting Corporation, Xinjiang Petroleum Administration Bureau and Institute of Petroleum Geological Sciences, Yunnan‐Guizhou‐Guangxi Petroleum Prospecting Bureau, 252Nanjing University Press.
4. Batyrbay Section, South Kazakhstan, U.S.S.R. – potential stratotype for the Cambrian–Ordovician Boundary