I'm blanking on the actual sources right now but I know that there is a growing trend in vet med to move away from cosmetic procedures like docking, cropping, and declawing. I'm in Canada but I just sent in a stack of surveys from my clinic stating how the vets there do not support declawing, do not perform the procedure, and try to educate clients away from it. In past jobs I simply refused to assist with those procedures.
When dealing with clients who want to declaw I find it useful to go over the exact procedure (multiple amputations), aftercare (good pain meds similar to those used after fracture repairs, bandages, etc), and the possibility of future health/behavioural issues. Following that I give my mini lecture on alternatives such as nail trims, Soft Paws, multiple scratching posts, and scratching deterrents. Many people simply have no idea what is involved in a declaw and are horrified when they discover what the surgery actually involves.
I'd love to read your letter once you're done with it.