Arya, D. J., E. H. Hiebert, and P. D. Pearson. “The Effects of Syntactic and Lexical Complexity on the Comprehension of Elementary Science Texts”. International Electronic Journal of Elementary Education, vol. 4, no. 1, Aug. 2017, pp. 107-25, https://iejee.com/index.php/IEJEE/article/view/216.