In Bava Basra 14b, a ברייתא is quoted as saying "Moshe wrote his book (i.e. the Pentateuch), Parashat Bil'am, and [the Book of] Iyov." Why did the ברייתא even raise the issue of Moshe's authorship of Parashat Bil'am?
Does "Parashat Bil'am" in the ברייתא refer to Parashat Balak, which speaks of Bil'am, or another book? If so, do we know more about this book?