Letter frequency references - douglasnaphas/cryptopals-py GitHub Wiki
- https://forum.tekgear.com/t/english-letter-frequencies-that-include-spaces-solved/112\
- http://norvig.com/mayzner.html
- https://link.springer.com/content/pdf/10.3758/BF03195586.pdf
- Answer lower on the page includes letter frequencies with space included: https://crypto.stackexchange.com/questions/30209/developing-algorithm-for-detecting-plain-text-via-frequency-analysis