Interpolation theorems for intuitionistic predicate logic

Craig interpolation theorem (which holds for intuitionistic logic) implies that the derivability of X,X’-¿Y’ implies existence of an interpolant I in the common language of X and X’-¿Y’ such that both X-¿I and I,X’-¿Y’ are derivable. For classical logic this extends to X,X’-¿Y,Y’, but for intuitionistic logic there are counterexamples. There is a version true for intuitionistic propositional (but not for predicate) logic, and more complicated version for the predicate case.