Natasha Grace Bartels, 'Beaker Problem', University of Albeda, Department of Anthropology, 1998 [1]
A Test of Non-metrical Analysis as Applied to the 'Beaker Problem' - Natasha Grace Bartels, University of Albeda, Department of Anthropology, 1998 [3]
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[2] Frase di Maria Gimbutas estrapolata da: Archaeology and language di Colin Renfrew, cap 3: Lost languages and forgotten scripts: The Indoeuropean languages, Old and New.