"Volcanoes". Columbia University. Consultado o 18 de xuño de 2019.
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Cross, Whitman; Iddings, Joseph P.; Pirsson, Louis V.; Washington, Henry S. (setembro de 1902). "A Quantitative Chemico-Mineralogical Classification and Nomenclature of Igneous Rocks". The Journal of Geology10 (6): 555–690. Bibcode:1902JG.....10..555C. doi:10.1086/621030.
Cross, Whitman; Iddings, J. P.; Pirsson, L. V.; Washington, H. S. (setembro de 1912). "Modifications of the "Quantitative System of Classification of Igneous Rocks"". The Journal of Geology20 (6): 550–561. Bibcode:1912JG.....20..550C. doi:10.1086/621996.
Cross, Whitman; Iddings, Joseph P.; Pirsson, Louis V.; Washington, Henry S. (setembro de 1902). "A Quantitative Chemico-Mineralogical Classification and Nomenclature of Igneous Rocks". The Journal of Geology10 (6): 555–690. Bibcode:1902JG.....10..555C. doi:10.1086/621030.
Cross, Whitman; Iddings, J. P.; Pirsson, L. V.; Washington, H. S. (setembro de 1912). "Modifications of the "Quantitative System of Classification of Igneous Rocks"". The Journal of Geology20 (6): 550–561. Bibcode:1912JG.....20..550C. doi:10.1086/621996.