@article{10_2140_agt_2006_6_2229,
     author = {Grbi\'c, Jelena and Wu, Jie},
     title = {Applications of combinatorial groups to {Hopf} invariant and the exponent problem},
     journal = {Algebraic and Geometric Topology},
     pages = {2229--2255},
     year = {2006},
     volume = {6},
     number = {5},
     doi = {10.2140/agt.2006.6.2229},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2006.6.2229/}
}