2631-2786 2631-2786 S2631-27862021000200151 10.35290/rcui.v8n2.2021.377 Ecuador 00 08 2021 00 08 2021 8 2 151 161

2001 4 9 9 71-85 2004 168 18-31 2003 2014 a 2014 b 2010 a 77-92 2010 b 77-92 1966 2008 1-17 2006 262-90 1982