I have a Contractor who maintains that an acceptable way of bonding/grounding a metal box used in a NM cable installation, would be to wrap the bare equipment ground wire around the screw that is used with the cable clamp. Now there are no cables under the clamp and the clamp is still installed so the bare wire is under the head of the screw and between the screw head and the clamp. I maintain that the Contractor should be using the 8-32 hole provided for installing a GREEN screw and not use the cable clamp screw what-so-ever for grounding. I don't think he should even use the silver colored cable clamp screw in the hole provided for the GREEN ground screw. I need something official for a reference. Thank You in advanc.