question about a sentence
1. what does " it bore the unmistakable JFK stamp"mean?
2.and in "which could be discerned in Kennedy’s first book", does this a book about Knnedy written by Ted Sorensen, or a book written by Kennedy?
context:
【They had been bouncing drafts back and forth for a week. It was an old routine, and although the result was joint authorship it bore the unmistakable JFK stamp, for Ted had adopted the literary style which could be discerned in Kennedy’s first book, published thirteen years before the two men met. 】