What are some good references for the Gauss composition law on binary quadratic forms in terms of Galois Cohomology?
It is my understanding that there is a cohomological approach, and I am studying for a comprehensive (oral) exam in which I will be presenting a talk on the topic in an effort to combine the three areas on which I will be examined: basic Algebraic Geometry (i.e. chapters II and III of Hartshorne); Algerbaic Topology (Spanier); and Number Theory (Samuel).
I guess to be more general, I should ask for an exposition in terms of etale cohomology, but the etale cohomology is exactly the Galois cohomology in the number field case anyhow.
Thanks!