Rings for Grain : An Interpretation for the Abundant Finds of the So-called "Ptolemaic Finger Rings" of the 3rd Century B.C. in the North Black Sea Area. - Ladynin, Ivan A. (Die Schätze der Erde :natürliche Ressourcen in der antiken Welt : Stuttgarter Kolloquium zur Historischen Geographie des Altertums 10, 2008, 2012)