W. Leigh Hadden, Ruth H. Watkins, Luis W. Levy, Edmundo Regalado, Diana M. Rivadeneira, Richard B. van Breemen & Steven J. Schwartz (1999). «Carotenoid composition of marigold (Tagetes erecta) flower extract used as nutritional supplement». Journal of Agricultural and Food Chemistry47 (10): 4189–4194. doi:10.1021/jf990096k. PMID10552789.
W. Leigh Hadden, Ruth H. Watkins, Luis W. Levy, Edmundo Regalado, Diana M. Rivadeneira, Richard B. van Breemen & Steven J. Schwartz (1999). «Carotenoid composition of marigold (Tagetes erecta) flower extract used as nutritional supplement». Journal of Agricultural and Food Chemistry47 (10): 4189–4194. doi:10.1021/jf990096k. PMID10552789.