@article{10_4064_sm187_1_3,
     author = {O. Bel Hadj Fredj and M. Burgos and M. Oudghiri},
     title = {Ascent spectrum and essential ascent spectrum},
     journal = {Studia Mathematica},
     pages = {59--73},
     year = {2008},
     volume = {187},
     number = {1},
     doi = {10.4064/sm187-1-3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm187-1-3/}
}