There was a DB Error:

Unknown table 'sp3' in where clause 

SELECT title1, title2, journal, citation
		, IF( id_doctype IN (4,6) , '' , title3 ) AS title3
      , IF(display_date <> ''
         , display_date
         , DATE_FORMAT(pub_date, "%M %D %Y")
       ) AS display_date 
FROM masterlist
WHERE id_doc = sp3.html