Police Enforcement Strategies to Prevent Crime in Hot Spot Areas / U.S. Department of Justice, Office of Community Oriented Policing Services
PDF - http://www.cops.usdoj.gov/files/RIC/Publications/e040825133-web.pdf
"The results of this systematic review support the assertion that focusing police efforts on high-activity crime places can be used to good effect in preventing crime. Seven of the nine evaluations reported noteworthy reductions in crime and disorder."