O. Umeji

Mid-Tertiary (late Eocene-early Miocene) lignites from Mpu Formation, Abakaliki Basin southwestern Nigeria

O. Umeji, 2002 .

Age control and designation of the standard stratotype of Nsukka formation of Anambra Basin, Southeastern Nigeria

O. Umeji, C. Nwajide, 2008 .

Palynological evidence of the Turunian / Campanian boundary between the Abakaliki and the Anambra basins, as exposed at Leru along the Enugu-Port Harcourt expressway, southeastern Nigeria

O. Umeji, 2007 .