12281Investigacion cientificaPT1993-07-13 17:56:00BT12331InvestigacionPTNT26124Investigacion cientifica (Africa)PTNT26125Investigacion cientifica (America)PTNT26126Investigacion cientifica (Asia)PTNT38249Investigación científica (Europa)PTNT13592Investigacion medicaPTNT8729MetodologiaPTRT8135Metodo cientificoPT