Quite simply put, any further "revelation" from Christ (this includes appearances, utterances, etc., are found in the Holy scriptures. Paul had many witnesses with him when God spoke. They heard a voice but saw no one(Acts 9:7). He also had Ananias, who was sceptical of Paul(Acts 10-17). The book of Mormon has never been accepted, even now, as Holy Scriptures. The Bible as we know, it apart from the book of Mormon, has been "tested" by the word of God itself and found to be authoratitive. This is called the canon. The books of the Bible are included in the canon. The canon are all of the books of the bible and no more . The canon means "these books" are the very words of God.