An umbilical point on a non-real-analytic surface Ando Naoya 広島大学 Hiroshima mathematical journal 00182079 33 1 1 14 2003-03 2003-03 110000016474 AA00664323 ENG NII-ELS 0 An umbilical point on a non-real-analytic surface Ando Naoya Hiroshima University Hiroshima mathematical journal Ando Naoya Department of Mathematics, Faculty of Science, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan