I have the following polynomial in $s$ $$\omega_4 s^4+\omega_3 s^3+\omega_2 s^2+\omega_1 s+\omega_0=0$$ where $\omega_i\in \mathbb R$ for $i=0,\dots,4$. This is a quartic equation and, as we can se on Wikipedia, there is a formula due to the italian mathematician Lodovico Ferrari.
Wikipedia article is very clear but I need also other types of references, like textbooks, papers etc. I read the references suggested by the above webpage but they are not as clear as Wikipedia.
I suggest the third chapter (“Quartic equations”) of Jean-Pierre Tignol's Galois' Theory of Algebraic Equations.