let F1, F2, F3, F4, G be MC-formula; :: thesis: ( {F1,F2,F3,F4} |-_IPC G implies {F2,F3,F4} |-_IPC F1 => G )
{F1,F2,F3,F4} = {F2,F3,F4} \/ {F1} by ENUMSET1:4;
hence ( {F1,F2,F3,F4} |-_IPC G implies {F2,F3,F4} |-_IPC F1 => G ) by Th53; :: thesis: verum