Alexandroff, Paul.
Elementary Concepts of Topology / translated by Alan E. Farley. - 1st ed / - New York 10014 : Dover Publications Inc, , 1982 - p.57 :
0-486-60747-X
Topology
B316 / K1A
Elementary Concepts of Topology / translated by Alan E. Farley. - 1st ed / - New York 10014 : Dover Publications Inc, , 1982 - p.57 :
0-486-60747-X
Topology
B316 / K1A