García-García, Inés, et al. “Erythrocyte Volume, Folate Levels, and the Presence of Methylenetetrahydrofolate Reductase Polymorphism”. Puerto Rico Health Sciences Journal, vol. 21, no. 1, Mar. 2013, https://prhsj.rcm.upr.edu/index.php/prhsj/article/view/907.