@article{Kominek:1974,
  author  = "Z. Kominek and J. Matkowski",
  title   = "On the existence of a convex solution of the functional equation $\varphi (x)=h(x,\,\varphi [f(x)])$",
  journal = "Annales Polonici Mathematici",
  volume  = "Vol. 30",
  pages   = "1--4",
  year    = "1974",
}