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I.  Teräs, ?Flower visits of bumblebees (Bombus: Hymenoptera, Apidae) during one day in northeastern Finland.?, Notulae Entomologicae, vol. 65, pp. 129-135, 1985.

I.  Teräs, ? Food plants and flower visits of bumblebees (Bombus: Hymenoptera, Apidae) in southern Finland?, Acta Zoologica Fennica, vol. 179, pp. 1-120, 1985.