3D Model Triangulation

I know, by reading some forum posts, that the triangulation process should be done manually before importing the 3d model into Unity to avoid the automatic process, which can be inefficient or maybe even wrong, but I haven't found any official statement from Unity itself. Do you know if there is one out there? Something like a "Best Practices" policy for 3d model import?

I need a "standard document" to serve as an orientation for our 3d modeler.