Kelvin made a youtube playlist for the correction clips. It is a great way to see common mistakes in student yilu.
To get a better understanding on how each students perform the yilu, please get the full videos from
http://practicalmethod.com/2010/10/yilu-corrections-online-video-purchase/
http://practicalmethod.com/2011/06/yilu-corrections-2-online-video-trailer/
