@article{Verbeeck:1225,
      author        = "Verbeeck, C. and Delouille, V. and De Visscher, R. and
                       Mampaey, B. and Haberreiter, M.",
      title         = "{Determination of filling factors of Active Regions,
                       Coronal Holes and Quiet Sun for the EIT archive 1997-2011}",
      year          = "2013",
}