reserve Y for TopStruct;
reserve X for non empty TopSpace;
reserve X for almost_discrete non empty TopSpace;

theorem Th60:
  ex M being Subset of X st M is maximal_discrete
proof
  set A = {}X;
  A is discrete by Th29;
  then consider M being Subset of X such that
  A c= M and
A1: M is maximal_discrete by Th59;
  take M;
  thus thesis by A1;
end;
