RT Article T1 COPS and crime JF Journal of public economics VO 91 SP 181 OP 201 A1 Evans, William N. A1 Owens, Emily A2 Owens, Emily LA English YR 2007 UL https://krimdok.uni-tuebingen.de/Record/1912493055 DO 10.1016/j.jpubeco.2006.05.014