Schubert (1949) showed that every knot can be uniquely decomposed (up to the order in which the decomposition is performed) as a knot sum of a class of knots known as prime knots, which cannot themselves be further decomposed (Livingston 1993, p. 5; Adams 1994, pp.
The Moors were Muslim inhabitants of the Maghreb, the Iberian Peninsula, Sicily, and Malta during the Middle Ages.
On Cornwall's moors and high ground areas the high elevation makes tree cover impossible because of the wind, so these areas are populated by shrubs and bushes such as gorse and heather. Ferns, mosses, liverworts, lichens and fungi can all be found in the county. In the wettest areas of Bodmin Moor, sphagnum or bog moss can be found. Cornwall is home to many rare flower species, especially at the southern end of the Lizard, due to its unique soil and geology.