@article{10_1090_S0894_0347_2012_00734_6,
     author = {Lian, Zeng and Young, Lai-Sang},
     title = {Lyapunov exponents, periodic orbits, and horseshoes for semiflows on {Hilbert} spaces},
     journal = {Journal of the American Mathematical Society},
     pages = {637--665},
     publisher = {mathdoc},
     volume = {25},
     number = {3},
     year = {2012},
     doi = {10.1090/S0894-0347-2012-00734-6},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-2012-00734-6/}
}