Miruts Hagos; Koeberl, C.; Jourdan, F. (2017). »Geochemistry and Geochronology of Phonolitic and Trachytic Source Rocks of the Axum Obelisks and Other Stone Artifacts, Axum, Ethiopia«. Geoheritage. 9 (4): 479–494. Bibcode:2017Geohe...9..479H. doi:10.1007/s12371-016-0199-7. S2CID132995691.
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Miruts Hagos; Koeberl, C.; Jourdan, F. (2017). »Geochemistry and Geochronology of Phonolitic and Trachytic Source Rocks of the Axum Obelisks and Other Stone Artifacts, Axum, Ethiopia«. Geoheritage. 9 (4): 479–494. Bibcode:2017Geohe...9..479H. doi:10.1007/s12371-016-0199-7. S2CID132995691.
Miruts Hagos; Koeberl, C.; Jourdan, F. (2017). »Geochemistry and Geochronology of Phonolitic and Trachytic Source Rocks of the Axum Obelisks and Other Stone Artifacts, Axum, Ethiopia«. Geoheritage. 9 (4): 479–494. Bibcode:2017Geohe...9..479H. doi:10.1007/s12371-016-0199-7. S2CID132995691.