1 | 18. BL: S.car* 19. t:S.car. mem_f(S.car;t;BL)  ( a:Alph. S.act(a,t) = u) AL:S.car*.
( s:S.car. mem_f(S.car;s;AL)  ( w:Alph*. mem_f(S.car;(S:w s);sL)))
& ( s:S.car. mem_f(S.car;s;sL)  u = s mem_f(S.car;s;TBL) mem_f(S.car;s;AL))
& ( s:S.car, a:Alph.
u = S.act(a,s) mem_f(S.car;S.act(a,s);TBL)  u = s mem_f(S.car;s;TBL) mem_f(S.car;s;AL)) |