@article{IM_1989__98_1_143744,
     author = {A. Katok and M. Pollicott and G. Knieper},
     title = {Differentiability and analycity of topological entropy for {Anosov} and geodesic flows.},
     journal = {Inventiones mathematicae},
     pages = {581--598},
     publisher = {mathdoc},
     volume = {98},
     number = {1},
     year = {1989},
     zbl = {0702.58053},
     url = {http://geodesic.mathdoc.fr/item/IM_1989__98_1_143744/}
}