0121-0807 0121-0807 S0121-08072018000200172 10.18273/revsal.v50n2-2018010 Venezuela 00 06 2018 00 06 2018 50 2 172 173 1. 2017 49 3 3 450-7 2. 2012 1-98 3. 2017 28 3 3 631-3 4. 1997 1a 17-8