0138-6557 0138-6557 S0138-65572021000200041 Peru 00 06 2021 00 06 2021 50 2 1 2020 49 4 4 1-14 2 2020 34 2 2 1-15 3 2020 28 1 1 237-62 4 2019 20 4 4 213-20 5 2017 4 5 5 1-11 6 2020 11 30 30 22-40