อ้างอิง

www.mtbk.ac.th/v.2009/technique%20of%20work/.../111.doc
mantarniwas.exteen.com/20071205/entry
board.dserver.org/t/thaipr01/00000328.html
learners.in.th/blog/khampom/357131
learners.in.th/blog/saowanee-seetussa/293995
www.nb2.go.th/~suwanpit/sc/project/.../CHEM_13.HTM
gotoknow.org/blog/mkj-work/201381