1. Carbon isotope fractionation in formation of amino acids by photosynthetic organism;Ableson,1961
2. Porphyrins in the geological record;Baker,1986
3. Diagenetic and catagenetic pathways for porphyrins in sediments;Barwise;Org. Geochem.,1984
4. Iron prophyrins in coal;Bonnett;J. Chem. Soc., Chem. Commun.,1983
5. Metalloporphyrins in lignite, coal, and calcite;Bonnett,1987