@article{RCM_1972__6_181594,
     author = {M. A. Guti\'errez},
     title = {Secondary invariants for links},
     journal = {Revista colombiana de matematicas},
     pages = {106--115},
     publisher = {mathdoc},
     volume = {6},
     year = {1972},
     zbl = {0254.57011},
     url = {http://geodesic.mathdoc.fr/item/RCM_1972__6_181594/}
}