@article{10_4153_CMB_2002_016_0,
     author = {Przytycki, J\'ozef H. and Rosicki, Witold},
     title = {The {Topological} {Interpretation} of the {Core} {Group} of a {Surface} in {S} 4},
     journal = {Canadian mathematical bulletin},
     pages = {131--137},
     year = {2002},
     volume = {45},
     number = {1},
     doi = {10.4153/CMB-2002-016-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2002-016-0/}
}