Herrera, E., Otero, E., Hincapié, L., Camacho, R., Gómez, G., Quintero, C., Guzmán, C. and Otero, P. (1) “Heterotopic pregnancy. Presentation of four cases”, Colombia Médica, 42(4), pp. 518-522. doi: 10.25100/cm.v42i4.953.