Have you tried any of the steps mentioned in the article? If not, I suggest starting with the 'Re-Introduction Technique,' where they'll be kept separate at first and then be re-introduced slowly. If that doesn't work, you can check with your vet to see if there's a medication he or she can give to help calm them down. If they are still fighting to the point of possibly getting injured after that, you might need to re-home one of them. But, I hope some of the suggestions in the article or from your vet can help, so that's not necessary. It does take some time, even months, for some cats to get to the point where they aren't fighting.