Cato Institute's 2nd Amendment Studies is a listing of some of the venerable think tank's pieces and commentary on the matter. In particular, Cato Policy Analysis No. 109 (though not linked to in the above page) is a classic study by Manhattan's former assistant district attorney David B. Kopel from July 1988. Cato Policy Analysis No. 284 from October 1997 is also quite good. Both are extensively well-sourced with complete citation information.