2477-9199 2477-9199 S2477-91992018000100120 10.26807/cav.v0i04.123 Ecuador 00 06 2018 00 06 2018 5 120 129

2004 2006 2009 2009 1996 2007 2005 2017 1992 2009 10 14 14 97-118