Reconstructing a single-head formula to facilitate logical forgetting

Logical forgetting may take exponential time in general, but it does not when its input is a single-head propositional definite Horn formula. Single-head means that no variable is the head of multiple clauses. An algorithm to make a formula single-head if possible is shown. It improves over a previous one by being complete: it always finds a single-head formula equivalent to the given one if any.