Charinthip Hengkrawit. 2009. Functional equations with trigonometric function solutions. Faculty of Science, Chulalongkorn University;
Charinthip Hengkrawit. (2009) Functional equations with trigonometric function solutions . Chulalongkorn University/Bangkok.
Charinthip Hengkrawit. Functional equations with trigonometric function solutions. . Bangkok:Chulalongkorn University, 2009.
Charinthip Hengkrawit. (2009) Functional equations with trigonometric function solutions . Chulalongkorn University/Bangkok.