@ARTICLE{Mueller:2010:Sky,
    author = {T. M{\"u}ller and D. Weiskopf},
    title = {{Distortion of the stellar sky by a Schwarzschild black hole}},
    journal = {Am. J. Phys.},
    year = {2010},
    volume = {78},
    pages = {204--214},
    doi = {10.1119/1.3258282}
}