- https://joachim-gassen.github.io/2020/03/meet-tidycovid19-yet-another-covid-19-related-r-package/
- https://mail-wolf.de/?p=4632
- https://joachim-gassen.github.io/2020/03/tidying-the-john-hopkins-covid-19-data/
- https://freakonometrics.hypotheses.org/60543
- https://blog.ephorie.de/covid-19-the-case-of-germany