Hello and welcome to FF! Mmmm, don't think frog snouts are of great taxonomic importance when identifying frogs. If your research paper is about different morphological snout differences across frogs, then would recommend linking the snout with the frogs mouth (i.e. the frogs feeding habits). For example, frogs that eat large prey (Pacmans, African Bullfrog) will have a large mouth and a different snout than frogs that eat little prey (i.e. ant/termite eating frogs). Also, some frogs will have a modified looking snout like the Pipa Pipa. If you search Google or Bing image section, can get pics of frogs and select those that have different snouts. Form those pictures, can get frog identification and with that conduct further research, good luck !