Porntip Thepmontar. (1999) Electronystagmography : a normative study in normal persons aged 20-40 years. Mahidol University,:ม.ป.ท.Porntip Thepmontar. 1999. Electronystagmography : a normative study in normal persons aged 20-40 years. ม.ป.ท.:Mahidol University,;Porntip Thepmontar. Electronystagmography : a normative study in normal persons aged 20-40 years. ม.ป.ท.:Mahidol University, 1999. Print.