Fernández, M. del C.C. 1964. Variation in the B-Carotene and Ascorbic Acid Contents of Lettuce and Carrots as Influenced by Seasonal Changes in Puerto Rico. The Journal of Agriculture of the University of Puerto Rico. 48, 1 (Jan. 1964), 39–48. DOI:https://doi.org/10.46429/jaupr.v48i1.12972.