 |  | Nigerian National Petroleum Corporation, Jul 2002 |
| | Nigerian National Petroleum Corporation, Mar 2001 |
| | Nigerian National Petroleum Corporation, Apr 2002 |
| | Nigerian National Petroleum Corporation, Jan- Mar 2000 |
| | Nigerian National Petroleum Corporation, Jan- Dec 1999 |
| | Nigerian National Petroleum Corporation, Feb 2002 |
| | Central Bank of Nigeria: Economic And Financial Review. Vol.34, No.3, Sep 1996 |
| | Nigerian National Petroleum Corporation, Aug 2002 |
| | Nigerian National Petroleum Corporation, Mar 2002 |
| | Nigerian National Petroleum Corporation, Jan 2001 |
