theorem for t0 being 0-termal string of S holds t0=<*S-firstChar.t0*>
proof
let t0 be 0-termal string of S;
reconsider e=(S-multiCat).(SubTerms(t0)) as empty set;
t0 = <*S-firstChar.t0*> ^ e by FOMODEL1:def 37 .= <*S-firstChar.t0*>;
hence thesis;
end;
