[PT] Question on a class of tautologies

Hello,

I would like to receive all sort of information regarding the 
following problem. If you answer to me exclusively, I'll then 
summarise to the list after a while.

PROBLEM   Characterise the set of classical propositional tautologies 
of the form A -> B such that:

* all and only the variables in A appear in B;
* no variable appears twice in A (and so in B);
* there is no negation in A and in B.

Cheers,

-Alessio