http://eslgrammartalk.blogspot.com.co/2009/02/grammartalk-8-pages-1-and-2-present.html
http://www.macmillaninspiration.com/original/files/2010/07/INSP3_ws8.pdf
http://learnenglish.britishcouncil.org/en/english-grammar/adjectives/adjectives-ed-and-ing
http://a4esl.org/q/h/9801/dg-eding.html