Low prevalence of vitamin D deficiency in adult residents in Hainan, the tropical island province of China - Lin, Leweihua; Ou, Qianying; Lin, Lu; Zhang, Huachuan; Chen, Kaining; Chen, Daoxiong; Quan, Huibiao; He, Yangli; Fang, Tuanyu (Annals of Palliative Medicine, 2021)