Where did I ask you about Nagarhara? Would you like to go back and read my post again? I simply asked you for a primary source for your assertion that KoBras migrated to the Konkan from the northwestern frontier. You have thus far provided none. Among the many theories I've read (most backed up by DNA/genetic evidence), none has been so specific as to suggest the exact area of their origin. You're apparently the only one who knows, and you have no basis for your claims. What do you mean by "primary source"? Do you want the name of the person who saw those princes being imprisoned? Do you want this witness to write a book? If not, and if you will accept contemporary sources which narrated the story, then those sources have already been provided. Now if you are asking how do we know those sources were right, well, there's obviously no way to know anything for sure until you travel back in time and witness the incident yourself. If the level of certitude required is such, then it will be impossible to prove anything at all.