@article{AM_1999_150_3_a10,
     author = {Ji-Ping Sha},
     title = {A secondary {Chern-Euler} class},
     journal = {Annals of mathematics},
     publisher = {mathdoc},
     volume = {150},
     number = {3},
     year = {1999},
     url = {http://geodesic.mathdoc.fr/item/AM_1999_150_3_a10/}
}