How to open up Electrolux Vacuum cleaner HELP!!!!?

Hope you can answer a question I have. How to open up Electrolux Vacuum cleaner to repair it? I have an older upright model Prolux also called a Epic. I have the bottom power head off. I just can’t get the tank part to open so I can replace or clean the fans on the motor. Its a great vacuum and worth fixing if I can just open it. This is my first upright; however I’ve been servicing my 1205 tank type for many years now. I need to know the trick for opening the body of my Prolux upright. Thanks for your help!
Thanks John

This is a link to a picture of the vaccum: http://www.cpsc.gov/cpscpub/prerel/prhtml99/99017.html