@article{10_4153_CJM_1968_076_7,
     author = {Hoo, C. S.},
     title = {Maps which {Induce} the {Zero} {Map} on {Homotopy}},
     journal = {Canadian journal of mathematics},
     pages = {759--768},
     year = {1968},
     volume = {20},
     number = {1},
     doi = {10.4153/CJM-1968-076-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-076-7/}
}