ATLANTA — Opponents of public money going toward new stadiums for the Atlanta Braves and Atlanta Falcons want lawmakers to require referendums for future public-private partnerships, even as those projects are underway. The Braves have begun construction of a new stadium in nearby Cobb County to replace downtown Turner Field, and the Falcons are building in downtown Atlanta next to the existing Georgia Dome. Public bonds have been approved for both — $200 million toward the Falcons $1 billion stadium and $300 million toward the Braves $672 million stadium.