Vitamin D level at birth and influencing factors in preterm infants
YU Ren-Qiang, ZHAO Xin, CHEN Dao-Zhen, LIAO Xiang-Peng, ZHOU Qin
CJCP . 2017, (7): 800 -805 .  DOI: 10.7499/j.issn.1008-8830.2017.07.014