Smoking and serum vitamin D in older Chinese people: Guangzhou Biobank Cohort Study Chao Qiang Jiang, MD, Guangzhou Number 12 Hospital;
Yap Hang Chan, Queen Mary Hospital;
Ya Li Jin, MD, Guangzhou Number 12 Hospital;
Lin Xu, PhD, The University of Hong Kong;
Kar Keung Cheng, PhD, University of Birmingham;
Tai Hing Lam, MD, The University of Hong Kong