@article{10_4153_CJM_1977_062_0,
     author = {Magill, Kenneth D.},
     title = {Homomorphisms from {S(X)} into {S(Y)}},
     journal = {Canadian journal of mathematics},
     pages = {615--625},
     year = {1977},
     volume = {29},
     number = {3},
     doi = {10.4153/CJM-1977-062-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1977-062-0/}
}