8/13/2019 2708966

1/7

http://www.jstor.org/action/showPublisher?publisherCode=upennhttp://www.jstor.org/page/info/about/policies/terms.jsphttp://www.jstor.org/stable/2708966?origin=JSTOR-pdfhttp://www.jstor.org/action/showPublisher?publisherCode=upenn

8/13/2019 2708966

2/7

8/13/2019 2708966

3/7

8/13/2019 2708966

4/7

8/13/2019 2708966

5/7

8/13/2019 2708966

6/7

8/13/2019 2708966

7/7