In my attempt to read the Bible through from cover to cover, I run across some strange things.
II Samuel 21:19 tells us that a man named Elhanan killed Goliath. The familiar story says David killed Goliath. I consulted my fundamentalist sources (Criswell Study Bible and Liberty (Fallwell) Bible) and found additional words, not in the original text of the KJV. These words are in italics. The introduction on using the Criswell Bible explains that words in italics are inserted to complete the mean of an obscure original text. So the italics tell us that Elhanan killed the brother of Goliath. Thus this verse is harmonized w/I Chr 20:5. The editors of the New Interpreters Study Bible tells us that the words about Goliath's brother were probably added by an original editor.
I can tell you that I do not like people adding words to the original text.