Ruth H. Watkins Birch, A. E., Fenner, G. P., Watkins, R., & Boyd, L. C. (2001). Antioxidant properties of evening primrose seed extracts. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, 49(9), 4502–4507. https://doi.org/10.1021/jf010542f Hadden, W. L., Watkins, R. H., Levy, L. W., Regalado, E., Rivadeneira, D. M., Breemen, R. B., & Schwartz, S. J. (1999). Carotenoid composition of marigold (Tagetes erecta) flower extract used as nutritional supplement. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, 47(10), 4189–4194. https://doi.org/10.1021/jf990096k Canjura, F. L., Watkins, R. H., & Schwartz, S. J. (1999). Color improvement and metallo-chlorophyll complexes in continuous flow aseptically processed peas. JOURNAL OF FOOD SCIENCE, 64(6), 987–990. https://doi.org/10.1111/j.1365-2621.1999.tb12265.x Emenhiser, C., Watkins, R. H., Simunovic, N., Solomons, N., Bulux, J., Barrows, J., & Schwartz, S. J. (1999). Packaging preservation of beta-carotene in sweet potato flakes using flexible film and an oxygen absorber. JOURNAL OF FOOD QUALITY, 22(1), 63–73. https://doi.org/10.1111/j.1745-4557.1999.tb00927.x Levy, L. W., Regalado, E., Navarrete, S., & Watkins, R. H. (1997). Bixin and norbixin in human plasma: Determination and study of the absorption of a single dose of Annatto Food Color. ANALYST, 122(9), 977–980. https://doi.org/10.1039/a701304c