Meckwell 2006
Preempt
2¨-DBL=Takeout
2¨-2©=5+©
2¨-2ª=5+ª
2¨-2NT=§+©
2¨-3§=5+§
2¨-3¨=©+ª
2¨-3NT=Natural
2¨-4§=6+©,Strong
2¨-4¨=6+ª,Strong