@article{White1992,
  author  = {S. R. White},
  title   = {Density matrix formulation for quantum renormalization groups},
  journal = {Phys. Rev. Lett.},
  volume  = {69},
  pages   = {2863},
  year    = {1992},
  doi     = {10.1103/PhysRevLett.69.2863},
}