1. S. K. Cherepanov, Botanical Material of Herbarium of the Komarov Botanical Institute AS USSR (Moscow-Leningrad, 1955), XVII, pp. 90–105 [in Russian].
2. E. Hultén, Flora of Kamtchatka and the Adjacent Islands (Stockholm, 1927).
3. E. Hultén, Flora of Alaska and Neighboring Territories (Stanford Univ. Press, California, 1968).
4. J. J. Furlow, Rhodora 81(826), 151 (1979).
5. J. J. Furlow, Flora of North America (Oxford Univ. Press, N.Y., 1997), 3, pp. 507–538.