reserve X for set;

theorem Th12:
  for S being SigmaField of X, T being N_Measure_fam of S holds ex
  F being sequence of S st T = rng F
proof
  let S be SigmaField of X, T be N_Measure_fam of S;
  consider F being sequence of bool X such that
A1: T = rng F by SUPINF_2:def 8;
  rng F c= S by A1,Def1;
  then F is sequence of S by FUNCT_2:6;
  then consider F being sequence of S such that
A2: T = rng F by A1;
  take F;
  thus thesis by A2;
end;
