Denjoy–Luzin–Saks theorem

In mathematics, the Denjoy–Luzin–Saks theorem states that a function of generalized bounded variation in the restricted sense has a derivative almost everywhere, and gives further conditions of the set of values of the function where the derivative does not exist. N. N. Luzin and A. Denjoy proved a weaker form of the theorem, and Saks (1937, theorem 7.2, page 230) later strengthened their theorem.

References

• Saks, Stanisław (1937), Theory of the Integral, Monografie Matematyczne, 7 (2nd ed.), Warszawa-Lwów: G.E. Stechert & Co., http://matwbn.icm.edu.pl/kstresc.php?tom=7&wyd=10&jez=pl