theorem Th35:
  for f1,f2 being Assign of BASSModel(R,BASSIGN) holds (for s being
  Element of S holds s|= f1 implies s|= f2) implies SIGMA(f1) c= SIGMA(f2)
proof
  let f1,f2 be Assign of BASSModel(R,BASSIGN);
  assume
A1: for s being Element of S holds s|= f1 implies s|= f2;
  let x be object;
  assume x in SIGMA(f1);
  then consider s be Element of S such that
A2: x=s and
A3: s|= f1;
  s|= f2 by A1,A3;
  hence thesis by A2;
end;
