1390-6542 1390-6542 S1390-65422017000100273 10.29019/enfoqueute.v8n1.128 Ecuador Ecuador 00 02 2017 00 02 2017 8 273 286

2013 511-25 2013 291-304 2017 2004 33 28 2007 13-24 2011 2010 2010 209-12 2008 3 2 2 1-23 2007 25-6 1996