@article{10_2140_agt_2005_5_725,
     author = {Pettet, Alexandra},
     title = {The {Johnson} homomorphism and the second cohomology of {IAn}},
     journal = {Algebraic and Geometric Topology},
     pages = {725--740},
     year = {2005},
     volume = {5},
     number = {2},
     doi = {10.2140/agt.2005.5.725},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2005.5.725/}
}