Eko, E. E. (1999). Effective writing. Heinemann Educational Books.
Cita Chicago (17th ed.)Eko, Ebele E. Effective Writing. Heinemann Educational Books, 1999.
Cita MLA (9th ed.)Eko, Ebele E. Effective Writing. Heinemann Educational Books, 1999.
Atenció: Aquestes cites poden no estar 100% correctes.