6/30/11 11 Software
John Barwise and John Etchemendy,  Language, Proof and Logic
This video shows extending, closing, and Analytical Consequence for a pretty advanced example tree. The tree itself is broad, spreading a long way from left to right. This leads to some scrolling back and forth because the applet is being held to the width of a printable page. [In the general case, though, the applet could be re-sized to take advantage of your no doubt sizable monitor and its extensive screen real estate.]
Please press the little triangle to play the video.