Yadarat Siramard. 1992. An investigation on the opinions of English teachers in the government secondary schools in educational region six in the academic year 1988 concerning the organizing of co-curricular English activities. Faculty of Graduate Studies, Mahidol University;

Yadarat Siramard. An investigation on the opinions of English teachers in the government secondary schools in educational region six in the academic year 1988 concerning the organizing of co-curricular English activities. . Bangkok:Mahidol University, 1992.

Yadarat Siramard. (1992) An investigation on the opinions of English teachers in the government secondary schools in educational region six in the academic year 1988 concerning the organizing of co-curricular English activities . Mahidol University/Bangkok.