I'm looking for a comprehensible reference that explains how $\Gamma$-spaces are related to $E_{\infty}$-operads. I've found some old publications but was hoping there are better references out there. Maybe a textbook or lecture notes?
By $\Gamma$-spaces I mean functors $\Gamma^{op} \rightarrow \textbf{Top}$ between the skeleton of the category of finite sets and the category of topological spaces $\textbf{Top}$.