WGET command line for download videos

I'm trying to figure out WGET for downloading some videos at http://windowsclient.net/learn/videos_wpf.aspx.

This page is an index page, and contains links to a page for each video; each page then has a direct link to a video. Something like;

http://windowsclient.net/learn/videos_wpf.aspx
  -> http://windowsclient.net/learn/video.aspx?v=300881
    -> http://download.microsoft.com/[...]/HDI-WPF-ipod-AccelerometerJoystick(2).mp4

What I'd like to do is tell WGET to spider the site by following either video.aspx?* or .mp4 links, recurively, for two levels. I can figure out

WGET -r -l2 http://windowsclient.net/learn/videos_wpf.aspx

and then I get stuck. Any suggestions greatly appreciated.

EDIT: Thanks to @mloskot, I got the answer;

WGET -r -l2 -A.mp4,video*.aspx* 
  --domains=windowsclient.net,download.microsoft.com 
  --span-hosts 

  http://windowsclient.net/learn/videos_wpf.aspx

Answer

Learn about option -A in the 2.11 and 4.2 chapter of wget manual and use this option to specify comma-separated lists of file name suffixes or patterns to accept. In other words, use -A to specify that you want to download only files with mp4 extension:

WGET -r -l2 -A.mp4 http://windowsclient.net/learn/videos_wpf.aspx