Actually, I figured it out myself. Here is the documentation.
The following quote is from this article.
Enron reported in its court filing yesterday that Citigroup's Citibank unit is its largest unsecured creditor, with two loans totaling $3 billion.
Leiberman's campaign contributions can be found at opensecrets.org. Click here and search on Lieberman
2002 Race for Senate: Citigroup $112,546 top contributor - (next was United Tech at $62000
2000 Race for Senate: Citigroup $59,296 top contributor - (next was United Tech at $36,000)
1998 Race for Senate: Citigroup $54,350 top contributor - (next was Goldman Sachs at $30,350)
The first time Citigroup shows up is in 1998 and, since then, they have been the top contributor.