@article{KohLeuL:03,
  journal = {Abstract and Applied Analysis},
  volume = 8,
  title = {{M}ann iterates of directionally nonexpansive mappings in hyperbolic
           spaces},
  author = {Kohlenbach, Ulrich and Leu\c stean, Laurentiu},
  year = 2003,
  pages = {449--477},
}