A great guide.
It's always worth clattering around the rim of the disc with a big hammer, turning as you beat the crap out of it. The slight deformation resultant from the sound thrashing breaks the rust bond and 'walks' the disk off the hub. This method only suitable if fitting new discs obviously.
Some recommend just cutting in with an angle dangler.
It will be all right in the end. If it isn't all right yet, then it is not yet the end..