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Winslow S. Caughey; James A. Ibers (1977). "Crystal and Molecular Structure of the Free Base Porphyrin, Protoporphyrin IX Dimethyl Ester". J. Am. Chem. Soc. 99 (20): 6639–6645. doi:10.1021/ja00462a027. PMID19518.
F. J. Leeper (1983). "The biosynthesis of porphyrins, chlorophylls, and vitamin B12". Natural Product Reports. 2 (1): 19–47. doi:10.1039/NP9850200019. PMID3895052.