RT Article T1 Measuring the informal economy: A validation study of the resource generation strategies scale JF Research on social work practice VO 17 IS 4 SP 466 OP 473 A1 Pyles, Loretta LA English YR 2007 UL https://krimdok.uni-tuebingen.de/Record/1912618869 DO 10.1177/1049731506296823