@article{10_4153_CMB_1977_016_x,
     author = {Freedman, H. I.},
     title = {On a {Bifurcation} {Theorem} of {Hopf} and {Friedrichs*}},
     journal = {Canadian mathematical bulletin},
     pages = {95--102},
     year = {1977},
     volume = {20},
     number = {1},
     doi = {10.4153/CMB-1977-016-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1977-016-x/}
}