@article{ASENS_1978_4_11_1_71_0,
     author = {Bourguignon, Jean-Pierre and Karcher, Hermann},
     title = {Curvature operators : pinching estimates and geometric examples},
     journal = {Annales scientifiques de l'\'Ecole Normale Sup\'erieure},
     pages = {71--92},
     publisher = {Elsevier},
     volume = {Ser. 4, 11},
     number = {1},
     year = {1978},
     doi = {10.24033/asens.1340},
     mrnumber = {58 #12829},
     zbl = {0386.53031},
     language = {en},
     url = {http://www.numdam.org/articles/10.24033/asens.1340/}
}