Where can I find a visual identification guide for business jets?

Large airliners are easy enough to identify and it is fairly simple to distinguish between a Gulfstream and a Falcon or a CJ and a Hawker. However, it is nearly impossible to tell the difference between a G500 and a G550. Sometimes there is no visual difference at all but sometimes when the manufacturer increases the fuel tank size he has to change the position of one of the lights on the wing. Stuff like that. I was wondering if there is some type of a guide book to this type of this. It would be great if it were accessible online but if not, that's ok.