theorem Th30:
  f in L1_CFunctions M & g in L1_CFunctions M implies (g a.e.cpfunc= f,M
  iff g in a.e-Ceq-class(f,M))
proof
  assume
A1: f in L1_CFunctions M & g in L1_CFunctions M;
  hereby
    assume g a.e.cpfunc= f,M;
    then f a.e.cpfunc= g,M;
    hence g in a.e-Ceq-class(f,M) by A1;
  end;
    assume g in a.e-Ceq-class(f,M);
    then ex r be PartFunc of X,COMPLEX st g=r & r in L1_CFunctions M & f in
    L1_CFunctions M & f a.e.cpfunc= r,M;
    hence g a.e.cpfunc= f,M;
end;
