1816-8949 1816-8949 S1816-89492020000200153 10.18004/anales/2020.053.02.153 Paraguay Paraguay 00 08 2020 00 08 2020 53 2 153 156

1 2006 14 172-87 2 2011 66 493-6 3 2011 19 S59-65 4 2013 26 90-3 5 2013 39 1577-87 6 2014 41 111-5