I will write an in depth article about this in the future, but for now, here are resources from other dog professionals:
Rebekah Piedad - Resource Guarding and the Myths that Surround the Behavior
Rebekah Piedad - Don't Sweat the Small Stuff: Minimizing Resource Guarding by Letting Stuff Go
Emily Larlham - Resource Guarding in Dogs
Dr Patricia McConnell - Resource Guarding Revisited (dog to human)
Dr Patricia McConnell - Resource Guarding, Dog to Dog (Repost)
Jean Donaldson - Mine! A Practical Guide to Resource Guarding in Dogs
Lili Chin - Constructional Aggression Treatment (C.A.T.)
Resource Guarding/Food Aggression (video)
Warning signals during resource guarding (dog body language lesson)