@article{JMLR:v11:rieck10a,
  author  = {Konrad Rieck and Tammo Krueger and Ulf Brefeld and Klaus-Robert M{{\"u}}ller},
  title   = {Approximate Tree Kernels},
  journal = {Journal of Machine Learning Research},
  year    = {2010},
  volume  = {11},
  number  = {16},
  pages   = {555--580},
  url     = {http://jmlr.org/papers/v11/rieck10a.html}
}