I mean simplifying a wff(well-formed formula)in which, only $\lor$, $\land$, $()$and $\lnot$ are allowed, as minimizing the occurence of connective symbols( $\land$ and $\lor$).
It's self-evident that there is no need to further simplifying wffs in which each variable only occurs once, say $A \lor B \land C$.
But it seems to me some other cases, like $(\lnot A_1 \land \lnot A_2) \lor(\lnot A_1 \land \lnot A_3) \lor(\lnot A_2 \land \lnot A_3) $ can't be simplified either.
My question is what is the rule determining whether a wff can be simplified?