@article{RCM_2017_51_2_a3,
     author = {Harold Contreras and B. Carlos Daniel Acosta},
     title = { Lorena {Aguirre,}},
     journal = {Revista colombiana de matematicas},
     pages = {195--220},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {2017},
     url = {http://geodesic.mathdoc.fr/item/RCM_2017_51_2_a3/}
}