Consistency of general bootstrap methods for degenerate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si26.gif" display="inline" overflow="scroll"><mml:mi>U</mml:mi></mml:math>-type and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si27.gif" display="inline" overflow="scroll"><mml:mi>V</mml:mi></mml:math>-type statistics