• DOI http://dx.doi.org/10.18177/sym.2011.51.itm.9493
  • PDF https://www.jstor.org/stable/26513072

  • PDF https://www.jstor.org/stable/41225256

  • PDF https://www.jstor.org/stable/41225254

  • PDF https://www.jstor.org/stable/41225239