:: deftheorem Def11 defines Stone-retraction TSP_2:def 11 :
for X being non empty TopSpace
for X0 being non empty maximal_Kolmogorov_subspace of X
for b₃ being continuous Function of X,X0 holds
( b₃ = Stone-retraction (X,X0) iff for a being Point of X holds b₃ . a in MaxADSet a );