Well that is always a hard one. I would say when Phoebe comes over to you and Norman jumps up, stop him in his tracks and tell him NO!! Plus keep Phoebe from going over, make her sit while you make Norman sit. Try to stop the fight before it begins. You have to show them both the same attention and try to find the triggers that set them off, and stop it before it begins. Sometimes the one you think is starting it, isn't the one after all, it was the other one. It just take time to study their body language to figure that out. I will tag @JeannieCO as she had a similar problem with two of hers and they get along very well now. Also @cali baker went through something similar with hers too.