YES 3: a() -> d() 5: f(c()) -> b() 6: d() -> c() @Jouannaud and Kirchner's criterion --- R 3: a() -> d() 5: f(c()) -> b() 6: d() -> c() --- S 3: a() -> d() 5: f(c()) -> b() 6: d() -> c() NOTE: input TRS is reduced original is 1: f(a()) -> b() 2: f(a()) -> f(c()) 3: a() -> d() 4: f(d()) -> b() 5: f(c()) -> b() 6: d() -> c() reduced to 3: a() -> d() 5: f(c()) -> b() 6: d() -> c()