What form do the doctors need to fill out to declare my mom mentally incapacitated?

I have been appointed durable power of attorney for finances for my mother through her living will. She has alzheimer's disease which is in the later stages. Her bank told me that I need to have two physicians declare her mentally incapacitated. I have made a doctor's appointment regarding this request. What form or statement should the doctors sign declaring that my mother is mentally incapacitated? Thanks very much for your advice.