@article{Matkowski:1993,
  author  = "J. Matkowski",
  title   = "Functions which are additive on their graphs and some generalizations",
  journal = "Rocznik Naukowo-Dydaktyczny WSP w Krakowie : Prace Matematyczne",
  number  = " 13",
  pages   = "233--240",
  year    = "1993",
  note = "",
}