Hi Julie. You need the ELI since K is a single letter abbreviation not followed by a period. Because K is an abbreviation, you should follow section 9f: The numeric indicator must be used after a hyphen when the hyphen follows a word, an abbreviation, or a mark of punctuation. Their examples include U-238 where the U is an abbreviation for Uranium (I guess)and the code book shows the use of both the ELI and the numeric indicator.