COMBINATORIAL PROBLEMS IN THE THEORY OF GRAPHS. I.

2 The abbreviation "i.o." indicates "infinitely often," that is, for infinitely many i. Similarly, in equations (6) and (16) it indicates that every point of C is covered by infinitely many Ai. 3 In the Lebesgue sense. 4Square brackets, here and in equation (17), denote the integral part. 6 R. von Mises, "'ber Aufteilungsund Besetzungswahrscheinlichkeiten, Revue de la Facultg des Sciences de l'Universite d'Istanbul, new ser., 4, 1-19, 1939. See also W. Feller, Probability Theory and Its A pplications, New York, 1950, p. 72, where a different proof is given.