@article{SPS_1988__22__89_0,
     author = {Yan, Jia-An},
     title = {A perturbation theorem for semigroups of linear operators},
     journal = {S\'eminaire de probabilit\'es de Strasbourg},
     pages = {89--91},
     publisher = {Springer - Lecture Notes in Mathematics},
     volume = {22},
     year = {1988},
     mrnumber = {960513},
     zbl = {0651.47030},
     language = {fr},
     url = {http://archive.numdam.org/item/SPS_1988__22__89_0/}
}