↑George, Edward Martin. The Foundations of Geometry and the Non-Euclidean Plane (İngilizce). s. 225. There is no branch of mathematics, however abstract, which may not some day be applied to phenomena of the real world.
↑Gudder, Stanley (1976). A Mathematical Journey (İngilizce). s. 36. There is no branch of mathematics, however abstract, which may not some day be applied to phenomena of the real world.