@article{DBLP:journals/apal/Wilken07,
  author    = {Gunnar Wilken},
  title     = {Ordinal arithmetic based on Skolem hulling},
  journal   = {Ann. Pure Appl. Logic},
  volume    = {145},
  number    = {2},
  year      = {2007},
  pages     = {130-161},
  ee        = {http://dx.doi.org/10.1016/j.apal.2006.07.003},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}