FOOTNOTES:
[59] In this chapter and the next, I owe much to the criticism and suggestions of Mr M. H. A. Newman of St. John's College, Cambridge, who must not, however, be held responsible for their contents; on me contrary, I am convinced that he could construct a much better theory than that which follows.
[60] Stetige Mengen, Monatshafte für Mathematik u. Physik., XXXI., 1921, pp. 173-204.
[61] Grundzüge der Mengenlehre, Leipzig, 1914.
[62] Ib., p. 211.
[63] Ib., p. 213.
[64] Zum Metrisationsproblem, Math. Annalen 94 (1925), pp. 309-315.
[65] He defines a topological space as "normal" when any two non-overlapping closed manifolds and can be separated by two non-overlapping regions , which respectively contain them and have no boundary-points. Ib., p. 310, and Hausdorff, op. cit., p. 215. A "boundary-point" of a collection is one which has a neighbourhood that is not a sub-class of the collection.