The campaign of Republican presidential frontrunner Mitt Romney doesn't follow the practice of other major presidential candidates who have willingly identified their big-money fundraisers and the amounts they collect.

But a review by The Associated Press of campaign records and other documents reveals hints about the vast national network of business leaders bringing in millions to elect Romney.

One example is the billionaire owner of the NFL's Miami Dolphins, Stephen Ross. Federal records show that Romney's campaign received $317,000 from nearly 150 people who share Ross's exclusive ZIP code on Florida's east coast. The same month, Ross invited friends and colleagues to his Palm Beach-area home for a Romney fundraiser.

The lack of transparency by the Romney campaign prevents voters from knowing who wields influence inside his campaign.