@article{Matkowski:2003,
  author  = "J. Matkowski",
  title   = "Affine and convex functions with respect to the logarithmic mean",
  journal = "Colloquium Mathematicum",
  volume  = "Vol. 95",
  number  = "no 2",
  pages   = "217--230",
  year    = "2003",
}