อ้างอิง

อ้างอิง

http://oss101.ldd.go.th/web_soils_for_youth/s_fertilizer.htm#chem

https://sites.google.com/site/chemeeci/xutsahkrrm-puy

http://www.scimath.org/socialnetwork/groups/viewbulletin/1198-?groupid=250

http://wit61.blogspot.com/2011/09/blog-post_02.html

http://www.krunid.com/board/index.php?topic=4590.0;wap2

http://www.scimath.org/socialnetwork/groups/viewbulletin/1197-?groupid=250

http://www.scimath.org/socialnetwork/groups/viewbulletin/1211-%E0%B8%9B%E0%B8%B8%E0%B9%8B%E0%B8%A2%E0%B8%9C%E0%B8%AA%E0%B8%A1?groupid=250

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