source: It has long been the economic centre of northern Nigeria, and a centre for the production and export of groundnuts.
target: It's historically the economic centre of northern Nigeria, and a centre for the production and export of groundnuts.
references: It's historically the economic centre of northern Nigeria, and a centre for the production and export of groundnuts. It is the business center and production and sending out of groundnuts.    of North Nigeria. It is the economic centre of Northern Nigeria and for the making and shipping of groundnuts. For a long time it has been the economic centre of Northern Nigeria.  It has also been a centre for the production and export of groundnuts. It has been the economic centre of northern Nigeria for a long time. It is also a centre for the production and export of groundnuts. It is the economic center of northern Nigeria. It is also a center for production and the export of groundnuts. It is the economic centre of northern Nigeria. It is the centre for the production and export of groundnuts. It has been the economic and groundnut centre of northern Nigeria for a long time. It is the economic and production of groundnuts centre of northern Nigeria. Northern Nigeria is the economic centre of production and export of groundnuts.