Are all of these references really non-canonical?
Does a reference to a non-canonical book exist just because there is similar language?  Some of Paul's so-called references seem to be little more than his borrowing of a turn of phrase.  In at least one case, a supposedly non-canonical source seems canonical to me.  Chronicles refers to a "book of Samuel, the seer" describing the deeds of King David.  Last I checked, there was a book in the bible accredited to Samuel, who was a seer, and that book was largely about the deeds of King David.  That got me wondering whether the book of Kings (like Chronicles and Samuel, usually published as two books in most modern bibles) records any of the other writings referenced in Chronicles.