I was wondering what good references there are for equivariant cohomology.

Specifically, I am working through the computation of $\text{H}^{\bullet}_{G(\mathcal{O})}(\text{Gr}_G)$ in http://arxiv.org/pdf/0707.3799v2.pdf (the bulk of this computation is done on page $8$, Section $3.1$). Here $G$ is a simple algebraic group, $\mathcal{O}=\mathbb{C}[[t]]$, $\mathcal{K}=\mathbb{C}((t)), \text{Gr}_G=G(\mathcal{K})/G(\mathcal{O})$.