Mere om Riemann
https://www.usna.edu/Users/math/meh/riemann.html , https://www.storyofmathematics.com/19th_riemann.html/

Mere om Cauchy

https://mathshistory.st-andrews.ac.uk/Biographies/Cauchy/

Mere om Wessel

https://mathshistory.st-andrews.ac.uk/Biographies/Cauchy/

Mere om komplekse tal

https://open.uct.ac.za/bitstream/handle/11427/31769/Mokhithi%20%26%20Shock%20_%20Complex%20Numbers%20v1.pdf?sequence=1

Mere om komplekse funktioner og Cauchy-Riemann ligningerne

https://nucinkis-lab.cc.ic.ac.uk/HELM/HELM_Workbooks_26-30/WB26-all.pdf