Variants of normality and their duals: a pointfree unification of insertion and extension theorems for real-valued functions
نویسندگان
چکیده
Katětov-Tong insertion type theorem For every upper semicontinuous real function f and lower semicontinuous real function g satisfying f ≤ g, there exists a continuous real function h such that f ≤ h ≤ g (Katětov 1951, Tong 1952). For every lower semicontinuous real function f and upper semicontinuous real function g satisfying f ≤ g, there exists a continuous real function h such that f ≤ h ≤ g (Stone 1949, Lane 1975).
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