Wikipedia contributors. (2023, November 7). Frederick William I of Prussia. In Wikipedia, The Free Encyclopedia. Retrieved November 8, 2023, from https://en.wikipedia.org/w/index.php?title=Frederick_William_I_of_Prussia&oldid=1183913890
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/people/f/frederick-william-i-of-prussia/en.wikipedia.org.snippet-relationship-with-frederick-ii-3-4.md