SAN FRANCISCO (Reuters) – Research restrictions pushed by the National Rifle Association have stopped the United States from finding solutions to firearms violence, more than a hundred scientists from virtually every major U.S. university told Vice President Joe Biden’s task force on gun violence in a letter on Thursday. In the wake of the December school massacre in Newtown, Connecticut, and other mass homicides, the group of economists, health researchers, educators, doctors and criminologists said funding should be restored to a range of study areas, from gun safety to tracking illegal …