Is there a compact, commonly used notation for indicating the reasons for an implication? For example, suppose I have previously established or been given $P$, and can use it to show that $B$ follows from $A$ because of $P$. I'd like to be able to write something like
$A \underset{P}\Rightarrow B,$
but feel like I'm making up notation that will not be understood. Is something like this common practice, and if so are there LaTeX conventions for generating it?