and a staple length of some the inner coat has a diameter of or sometimes less, with a staple length in the range The two types may be used separately, or spun into a single yarn, lopi, a soft wool which provides good insulation. Notes References Further reading Stefán Aðalsteinsson (1970). Colour inheritance in Icelandic sheep and relation between colour, fertility and fertilization. Journal of Agricultural Research, Iceland. 2 (1): 3–135. Stefán Aðalsteinsson (1975). Depressed fertility in Icelandic sheep caused by a single colour gene. Annales de génétique et de sélection animale. 7 (4): 445. Stefán Aðalsteinsson (1977). Albinism in Icelandic sheep. The Journal of Heredity. 68 (6): 347–349. . Stefán Aðalsteinsson (1983). Inheritance of colours, fur characteristics and skin quality traits in North European sheep breeds: a review. Livestock Production Science 10:555-567. Jón V. Jónmundsson, Stefán Aðalsteinsson (1985). Single genes for fecundity in Icelandic sheep. In: R.B. Land, D.W. Robinson (1985). Genetics of Reproduction in Sheep. London: Butterworths. , pages 159–168. . Sheep breeds Sheep breeds originating in Iceland