@article{Grytczuk:2000,
  author  = "A. Grytczuk and F. Luca and M. Wójtowicz",
  title   = "On a conjecture of Makowski and Schinzel concerning the composition of the arithmetic functions \delta and \fi",
  journal = "Colloquium Mathematicum",
  volume  = "Vol. 86",
  number  = "no 1",
  pages   = "31--36",
  year    = "2000",
}