Zhang, X., Ding, F., Li, H., Zhao, W., Jing, H., Yan, Y., & Chen, Y. (2016). Low Serum Levels of Vitamins A, D, and E Are Associated with Recurrent Respiratory Tract Infections in Children Living in Northern China: A Case Control Study. PLoS One.

Zhang, Xuguang, Fengshu Ding, Huaining Li, Wenfeng Zhao, Hong Jing, Yageng Yan, and Yanping Chen. "Low Serum Levels of Vitamins A, D, and E Are Associated With Recurrent Respiratory Tract Infections in Children Living in Northern China: A Case Control Study." PLoS One 2016.

Zhang, Xuguang, et al. "Low Serum Levels of Vitamins A, D, and E Are Associated With Recurrent Respiratory Tract Infections in Children Living in Northern China: A Case Control Study." PLoS One 2016.