Vorlage:Blieck et al., 1991

• Blieck, A. R. M., Elliott, D. K. & Gagnier, P.-Y.  1991. Some questions concerning the phylogenetic relationships of heterostracans, Ordovician to Devonian jawless vertebrates. Pp. 1–17 in  Chang, M.-M., Liu, Y.-h. &  Zhang, G.-r. (eds.): Early vertebrates and related problems of evolutionary biology. Beijing: Science Press.