Household secondhand smoke exposure of elementary schoolchildren in Southern Taiwan and factors associated with their confidence in avoiding exposure: a cross-sectional study oleh Huang Hsiao-Ling, Yen Yea-Yin, Lin Pi-Li, Chiu Chin-Hsuan, Hsu Chih-Cheng, Chen Ted, Hu Chih-Yang, Lin Ya-Ying, Lee Chien-Hung, Chen Fu-Li