theorem :: SETFAM_1:8
  G in sf & G c= H implies Intersect sf c= H
proof
  assume that
A1: G in sf and
A2: G c= H;
  Intersect sf = meet sf by A1,SETFAM_1:def 9;
  hence thesis by A1,A2,SETFAM_1:7;
end;
