Citations for tonight's show are listed after the jump.
Documents establishing purchase of rifle by Lee Harvey Oswald
Ed Markey Invokes Newtown In Massachusetts Senate Primary Ad
The Clergy Leaders of Newton ad (pdf)
Post-ABC poll: Gun control politics
What's Romney Hiding in His Tax Returns?
What might be hiding in Romney's tax returns?
Why Mitt Romney won't release his tax returns: 6 theories
Boehner, Ryan: Romney's Taxes a Grand Distraction
Ryan Plan Revives '12 Election Issues
Paul Ryan's House budget echoes Republican vision from 2012
Gillespie: Romney tax plan specifics will come after election
Global Temperatures Highest in 4,000 Years
In Study, Past Decade Ranks Among Hottest
Tesla repaying Obama admin loan 5 years early
Santorum sweeps South: wins Alabama and Mississippi
Romney sweeps five wins, promises 'better America'
Romney wins primaries in Nebraska, Oregon
Full video and transcript of leaked Romney fundraiser remarks
SECRET VIDEO: Romney Tells Millionaire Donors What He REALLY Thinks of Obama Voters