:: Dyadic Numbers and $T_4$ Topological Spaces :: by J\'ozef Bia\las and Yatsuka Nakamura :: :: Received July 29, 1995 :: Copyright (c) 1995-2012 Association of Mizar Users
uniqueness
for b1, b2 being Subset of REAL st ( for x being Real holds ( x in b1 iff ex i being Nat st ( i <= 2 |^ n & x = i /(2 |^ n) ) ) ) & ( for x being Real holds ( x in b2 iff ex i being Nat st ( i <= 2 |^ n & x = i /(2 |^ n) ) ) ) holds b1= b2
redefine attr T is T_1 means :Def7: :: URYSOHN1:def 7 for p, q being Point of T st not p = q holds ex W, V being Subset of T st ( W is open & V is open & p in W & not q in W & q in V & not p in V );
:: Some increasing family of sets in normal space
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