Quite correct.
Not just delta winged a/c either. Canard types can't have them either - unless the canard also has some lift enhancing mechanism so that the overall CoP (canard+mainplane) doesn't move significantly eg the Beech Starship canard/pusher turboprop.
Delta winged types can often make use of much higher AoA than conventional aerofoils, along with a method of lift production using a large vortex shed from the forward wing root area.
[ 19 July 2001: Message edited by: Tinstaafl ]