@article{Drzewiński:1990,
  author  = "A. Drzewiński and J. Sznajd",
  title   = "Quantum XY and Heisenberg models on the planar lattices - the renormalization group approach",
  journal = "Physica B",
  volume  = "Vol. 165-166",
  pages   = "223--224",
  year    = "1990",
}