Virat Poonsup. 1991. An economic planning for crop production under a certain situation and risk in agro-economic zone 6. Graduate School, Kasetsart University;
Virat Poonsup. (1991) An economic planning for crop production under a certain situation and risk in agro-economic zone 6 . Kasetsart University/Bangkok.
Virat Poonsup. An economic planning for crop production under a certain situation and risk in agro-economic zone 6. . Bangkok:Kasetsart University, 1991.
Virat Poonsup. (1991) An economic planning for crop production under a certain situation and risk in agro-economic zone 6 . Kasetsart University/Bangkok.