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on September 18, 2010
“English Grammar—Tenses” Retrieved from
http://www.englisch-hilfen.de/en/grammar_list/zeitformen.htm
on September 18, 2010
“Learning English online” Retrieved from
http://ict.moph.go.th/English/content/verb02_tense.htm
on September 18, 2010
“Verb tenses tutorial” Retrieved from
http://www.englishpage.com/verbpage/verbtenseintro.html
on September 18, 2010
“Oxford Headway” Retrieved from http://www.oup.com/elt/global/products/headway/preintermediate/a_grammar/unit01/
hwy_preint_unit01_1/
on September 18, 2010
