E.  Ranta, Teräs, I., and Lundberg, H., ?Phenological spread in flowering of bumblebee-pollinated plants?, Annales Botanici Fennici, pp. 229-236, 1981.

E.  Ranta, Lundberg, H., and Teräs, I., ?Patterns of resource utilization in two Fennoscandian bumblebee communities?, Oikos, vol. 36, pp. 1-11, 1981.