I'm becoming very interested in collecting Disney Dollars so can anyone tell me if there is a guide or any publication on these? Looking at ebay and various sites I can see that at least the 87 thru 90 bills all have the same obverse with slight differences. On ebay there are people selling tthe 88's & 89's as 87's, so I need to become educated on these if I'm going to jump in. Thanks for any help.