Callmer, J. (1977). Trade beads and bead trade in Scandinavia, ca. 800-1000 A.D. Rudolf Habelt Verlag.
Lua i Stíl Chicago (17ú heag.)Callmer, Johan. Trade Beads and Bead Trade in Scandinavia, Ca. 800-1000 A.D. Bonn: Rudolf Habelt Verlag, 1977.
Lua MLA (8ú heag.)Callmer, Johan. Trade Beads and Bead Trade in Scandinavia, Ca. 800-1000 A.D. Rudolf Habelt Verlag, 1977.
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