"and had been seeking to negotiate a surrender through various methods and channels for months prior to the dropping of the bombs"
Well, as to sources, there's a ton of them.
- Dirty Little Secrets of World War II and Victory At Sea (James Dunnigan and Alfred A. Nolfi)
- The Two Ocean War (History of the United States Navy 1941-45) Samuel Elliot Morrison
- The Penguin History of the Second World War (Calvocoressi, Wint and Pritchard). Calvocoressi, incidentally, was a codebreaker at Bletchly Park. This is the DEFINITIVE Book on the politics of the Second World War, in my opinion.
Those will do just to begin with. If you want more, I'll be more than happy to provide them for you.