theorem
for F being 0-characteristic Field,
    E being Field st F includes E holds E includes F_Rat
proof
let F be 0-characteristic Field, E be Field;
assume F includes E;
then F is E-monomorphic by Th71;
then Char E = Char F by Th87 .= 0 by Def6;
then E is 0-characteristic;
hence thesis by Th71;
end;
