TY - JOUR AU - Brodersen, N H; Steptoe, A; Boniface, D R TI - Trends in physical activity and sedentary behaviour in adolescence: ethnic and socioeconomic differences JO - Br J Sports Med VL - 41 PY - 2007 DO - 10.1136/bjsm.2006.031138 L3 - PubMed-ID: 17178773 SP - 140 EP - 144 N1 - et al. ER -