Wichian Sittiprapaporn. 1997. A Thai dialect geography of Udonthani province : a tonal study. , Mahidol University;
Wichian Sittiprapaporn. (1997) A Thai dialect geography of Udonthani province : a tonal study . Mahidol University/Bangkok.
Wichian Sittiprapaporn. A Thai dialect geography of Udonthani province : a tonal study. . Bangkok:Mahidol University, 1997.
Wichian Sittiprapaporn. (1997) A Thai dialect geography of Udonthani province : a tonal study . Mahidol University/Bangkok.