@Article{Zhou06,
  author =  {Zhou, J. and Luo, L. M.},
  title =   {{Sequential weighted least squares algorithm for {PET} image reconstruction}},
  journal = {Digital Signal Processing},
  year =    {2006},
  volume =  {16},
  pages =   {735--745},
  doi =     {10.1016/j.dsp.2006.08.006}
}