Two-phase linear relationship of Vitamin D and Vitamin A among children aged 0–14 years: a cross-sectional study - Liu, Wenyuan; Wang, Qiao; Mao, Bibo; Xu, Fei; Ke, Yefang; Zhang, Shengying; Zhou, Chenbo; Liu, Chunyan; Lu, Wenbo; Zheng, Jishan (Frontiers in Nutrition, 2025)