Kumaran, K.P. Navaneetha, J.J. Edet, and E.E. Nyong. 1993. “A Reappraisal of Salviniaceous Fossils and Its Implication on the Age and Depositional Environment of Nkporo Shale of Calabar Flank, Nigeria”. Journal of Palaeosciences 42 (1-3):210-14. https://doi.org/10.54991/jop.1993.1148.