@techreport{murrell-visual-testing-2020,
  title="Visual Testing for Graphics in R",
  author = {Paul Murrell},
  year={2020},
  note={version 1},
  institution={Department of Statistics, The University of Auckland},
  number={2020-01},
  url={https://stattech.wordpress.fos.auckland.ac.nz/2020/01/06/2020-01-visual-testing-for-graphics-in-r},
  doi={http://doi.org/10.17608/k6.auckland.11521212}
}