Special thanks to Matthew Loftus for reviewing the math in our story!

Sources:

The Mathematics of Sonya Kovalevskaya, Roger Cooke, 1984

Remarkable Mathematicians: From Euler to Von Neumann, Ioan James, 2003

A Russian Childhood, Sofya Kovalevskaya, 1978

Queered Science: ¬†Historic Women Pioneers,” Autostraddle, by Vivian; you can see the actual photo of Sofia and Anne-Charlotte there!

“A Brief History of Romantic Friendship,” Brain Pickings, by Maria Popova; not directly about Sofia but about the term “Romantic Friendship,” which was a term way back when!

http://biography.yourdictionary.com/sophia-vasilevna-kovalevsky

http://www-history.mcs.st-and.ac.uk/Biographies/Kovalevskaya.html

http://www-math.ucdenver.edu/~wcherowi/courses/m4010/s08/klkovalevkaya.pdf