Appendix

Abstract

Trying to make the book self-contained, in Sections 11.1 and 11.2 we recall some well-known notions and their properties. A reader need not read those sections. If she/he needs to recall something, she/he can use the Index to find it. Section 11.3 summarizes well-known facts from elementary topology showing the close connection between the notions of a compact topological space and the real line. Finally, in Sections 11.4 and 11.5 we summarize basic facts of mathematical logic and main results of the theory of models of set theory. The latter are intensively used in the basic text.