# Fermat's Two Squares Theorem/Historical Note

According to Ivan M. Niven, on "Albert Girard" at Absolute Astronomy.com, Fermat's Two Squares Theorem was initially stated without proof by Albert Girard in $1632$.
Fermat announced its proof in a letter to Marin Mersenne dated December $25$, $1640$.
The first published proof was by Leonhard Paul Euler after $7$ years of hard work.