Ho w do you get into a canoscan 3200f?

Hi I have a canoscan 3200 f which has dust on the inside of the glass,
Question is how do you seperate the top from th ebottom.

There are two small screws at the back and a small pplate to give access to the ribbon cable but unless the are under the rubber feet I can find no other screws.

Any ideas Guys

Your help would be much appreciated

Regards
John

John
June 2009