Bowman, J. C., Zeiler, A., & Biskamp, D. (2000). A Multigrid Algorithm for Nonlocal Collisional Electrostatic Drift-Wave Turbulence. Journal of Computational Physics, 158, 239-261. Retrieved from http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WHY-45F4WH7-N-1&_cdi=6863&_user=100196&_orig=browse&_coverDate=03%2F01%2F2000&_sk=998419997&view=c&wchp=dGLbVzz-zSkzS&md5=43bb958579eff6d70113b5634d0e33bc&ie=/sdarticle.pdf.