This is not controversial stuff; this is like asking if I've got documentation that Truman was once president. The whole negotiation debacle is in any reputable history text of that period; just look it up. Encyclopedia, even. (It's also on wikipedia, but I don't consider that a great source.)

The debate is not whether we could've accepted a surrender without arresting the Emperor; that's fact. The debate is whether or not the Japanese would have actually kept to their terms, without the bombs. If you think the Japanese would've fought to the last man despite Hirohito's opposition, the desire for peace on the war council and the assassination of two prime ministers in short order during that time when they began to talk about peace, then you're right to support the bombs. I happen to think you're wrong.