There are two videos from Dinosaur Planet for movie Monday which fit our needs of describing and showing O. mongoliensis. The videos do not make a differentiation between O. philoceratops and O. mongoliensis, however, O. mongoliensis skulls have a more definitive crest than O. philoceratops which is more like that presented in the videos below. The third species they mention is Ingenia yanshini. Since I don't own the videos and they aren't on youtube I can't paste them directly in here; no embedding feature on the site they're on.
Oviraptor video #1
Oviraptor video #2