There are two ways to do it, I hit the bottom of the floor with a hammer and made the floor flex (not dent) and it would come off in chunks.  In the spots that I coudnt get under with the hammer I used a heat gun and putty knife (MESSY)  If I was to do it again Id get a couple lbs. of dry ice and cover the floor with it then it would come up in huge pieces Im sure.