http://digfir-published.macmillanusa.com/gls_animated_graph/gls_6_2.html\tChapter 1. eFigure 6.2 \t5150b6b3b11c0f3858000001 http://digfir-published.macmillanusa.com/gls_animated_graph/gls_6_2_dlap.xml\tDLAP questions\t5150b6b3b11c0f3858000001