Figure 4From: Characterization and Identification of Natural Terpenic Resins employed in “Madonna con Bambino e Angeli” by Antonello da Messina using Gas Chromatography–Mass Spectrometry Mass spectra and molecular structures of dehydroabietic acid methyl ester (a) and 7-oxo-dehydroabietic acid methyl ester (b). Back to article page