Nan, please go to the club database at http://www.glass411.info. As a suggestion, search for Shell as entry 1 and NFL as entry 2. You'll find a list of the small and tall smoked sets from Shell that are from circa 1972. There are many other sets from Mobil in the 70's, and later sets as well. Some of the entries do not have a picture at this time. There is some debate among most collectors as to the existence of certain teams, but there are several collectors in the club who could absolutely verify what cities (or if all) were represented. If memory serves, there may have been a club article in the past as well, but perhaps someone else can chime in with that info.
Hope that helps!
Steve