@article{10_2140_agt_2014_14_91,
     author = {Han, Fei and Liu, Kefeng},
     title = {Gravitational anomaly cancellation and modular invariance},
     journal = {Algebraic and Geometric Topology},
     pages = {91--113},
     year = {2014},
     volume = {14},
     number = {1},
     doi = {10.2140/agt.2014.14.91},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2014.14.91/}
}