00250nam a2200097 a 4500041000800000082001800008100002800026245004500054260004400099300000900143  aspa  a305.56bT566e  aTorres Rivas, Edelberto  aEstructuras sociales en América Latina  aBuenos AiresbUNESCObCEPALbPNUDc1981  a90 p