@article{AIF_1970__20_1_317_0,
     author = {Walsh, Bertram},
     title = {Perturbation of harmonic structures and an index-zero theorem},
     journal = {Annales de l'Institut Fourier},
     pages = {317--359},
     publisher = {Institut Fourier},
     address = {Grenoble},
     volume = {20},
     number = {1},
     year = {1970},
     doi = {10.5802/aif.344},
     mrnumber = {43 #554},
     zbl = {0187.04303},
     language = {en},
     url = {http://www.numdam.org/articles/10.5802/aif.344/}
}