Prof M.Bhargava's work on "Higher Composition Law" which solved some outstanding conjectures on number theory seems to be very interesting topic. I have seen his papers but, in spite of the titles, it is not easy to understand (Of course in my point of view, for sure there are many people who can understand it easily).

Do you know any lecture note or expository paper which explains more details and some explicit example? especially his work on composition law for binary quadratic form.

Thanks