@article{GFA_1993__3_6_58139,
     author = {N. Anghel},
     title = {On the {Index} of {Callias-type} {Operators.}},
     journal = {Geometric and functional analysis},
     pages = {431--438},
     publisher = {mathdoc},
     volume = {3},
     number = {6},
     year = {1993},
     zbl = {0843.58116},
     url = {http://geodesic.mathdoc.fr/item/GFA_1993__3_6_58139/}
}