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Kreutz, Barbara M. (July 1973). «Mediterranean Contributions to the Medieval Mariner's Compass». Technology and Culture14 (3): 373. JSTOR3102323. doi:10.2307/3102323. (note 21)
Kreutz, Barbara M. (July 1973). «Mediterranean Contributions to the Medieval Mariner's Compass». Technology and Culture14 (3): 373. JSTOR3102323. doi:10.2307/3102323. (note 21)