求助英文文献两篇：

第一篇篇名：Values, environmental concern, and environmental behavior: a study into household energy use。

作者：Poortinga, W., Steg, L., Vlek, C.      2004.

Environment and Behavior 36, 70–93。

第二篇篇名：The role of problem awareness in willingness-to-change car use and in evaluating relevant policy measures。

作者：Steg, L., Vlek, C      1997

Theory and Application. Pergamon, Oxford, pp. 465–475.