Active vs passive voice
http://www.youtube.com/watch?v=ePfmgMTgXl8
Making negatives
http://www.youtube.com/watch?v=JTdnAkhAOyc
Passive voice
http://www.youtube.com/watch?v=fbOVVE2PoLk
Reported speech
http://www.youtube.com/watch?v=mvgJ1OAxruw
http://www.youtube.com/watch?v=ePfmgMTgXl8
Making negatives
http://www.youtube.com/watch?v=JTdnAkhAOyc
Passive voice
http://www.youtube.com/watch?v=fbOVVE2PoLk
Reported speech
http://www.youtube.com/watch?v=mvgJ1OAxruw