@Article{ 
  mag,
  author = { Magnani, Valentino },
  title = { On a general coarea inequality and applications },
  journal = {  Ann. Acad. Sci. Fenn. Math. },
  year = { 2002 },
  volume = { 27 },
  pages = { 121-140 },
  URL = { http://cvgmt.sns.it/paper/708/ },
  note = { cvgmt preprint}
}