@article{10_1017_S0017089500001713,
     author = {Berndt, Bruce C.},
     title = {An elementary proof of some character sum identities of {Apostol}},
     journal = {Glasgow mathematical journal},
     pages = {50--53},
     year = {1973},
     volume = {14},
     number = {1},
     doi = {10.1017/S0017089500001713},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500001713/}
}