1. Closed connected sets which are disconnected by the removal of a finite number of points, Proceedings of the National Academy, vol. 9 (1923), pp. 7–12.
2. IfP is a point of a connected setM, P is said to be a cut point of powern ifM—P consists of exactlyn components.
3. ε′ denotes that the summation is over all values included between the limits except zero.
4. IfX is any point of an open curveC, the setC—X consists of two components or maximal connected subsets. Each of these components plus the pointX is called a ray andX is said to be the vertex of each ray. Or a ray may be defined as a closed point set in continuous (1,1) correspondence with those points of thex-axis for whichx is non-negative.
5. B. Knaster and C. Kuratowski, Sur les continus non-bornés. Fund. Math., vol. 5 (1924), p. 26.