@article{MV_1978_30_1_a21,
     author = {B. K. Ray},
     title = {On quasi-contraction mappings in {Banach} spaces},
     journal = {Matemati\v{c}ki vesnik},
     pages = {159 },
     year = {1978},
     volume = {30},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/MV_1978_30_1_a21/}
}