@misc{indiciae681b5c1da1f1,
  title = {A Simple Calculus for Discrete Systems, Part B},
  author = {Leonard, J. N. and Pixley, A. F. and Wulff, J. J.},
  year = {1968},
  url = {https://ntrs.nasa.gov/citations/19680004795},
  note = {Source identifier: 19680004795}
}