If you read Roberts's opinion he literally explains the definition of jurisdiction as it stood when the amendment was drafted (he cites three different dictionaries) and cites floor arguments directly from the Congressional record. It's not long, takes about 15 minutes to get through.

The rest of the documents are the concurrences (Jackson) and the three, frankly insane, dissents. Thomas's is 90 pages long somehow (I couldn't get through all that one, it's properly crazy).