Wannarut Chutibut และ Jariya Wongtree; Thongchan Pimpet; Chadaporn Khongnam; Omara Hanjavanich; Jariya Prasatsrisupub; Sunantha Chompoonich. (2009) Proficiency Testing in Chemical Fertilizer Analysis. <i>Thai Agricultural Research Journal</i>, <i>27</i>(1), 43-54.Wannarut Chutibut และ Jariya Wongtree; Thongchan Pimpet; Chadaporn Khongnam; Omara Hanjavanich; Jariya Prasatsrisupub; Sunantha Chompoonich. "Proficiency Testing in Chemical Fertilizer Analysis". Thai Agricultural Research Journal 27 (2009):43-54.Wannarut Chutibut และ Jariya Wongtree; Thongchan Pimpet; Chadaporn Khongnam; Omara Hanjavanich; Jariya Prasatsrisupub; Sunantha Chompoonich. Proficiency Testing in Chemical Fertilizer Analysis. Department of Agriculture:ม.ป.ท. 2009.