Who has given root canal isthmus classification?

Kim et al Classification Root apex cross-section Narrow ribbon-shaped connection that contains pulp or pulpally derived tissue - ISTHMUS According to Kim et al classification; there are 5 types: Type I : Incomplete isthmus between 2 canals. Type II : Well defined, complete isthmus between 2 canals. Type III : Very short, but complete isthmus between 2 canals. Type IV : 3 or more canals with the complete or incomplete isthmus. Type V : 3 or more canals without any visible connection.