The Text
The Senate shall consist of three Senators from each State and one from the Federal Capital Territory, Abuja.
Source · Constitution of the Federal Republic of Nigeria, 1999, as amended · §48
All sections in Chapter V — The Legislature
Methodology
Tier 1 · primary
Courts. Gazettes. National archives.
Tier 2 · corroborating
OCCRP. HRW. BudgIT. TheCable.
Redline
Wikipedia is never a source.