When I nest a query within another query I am getting the error “SQL error 1241 operand should contain 5 column(s)”

Question

SELECT *
FROM AUTHOR
WHERE FLOOR(DATEDIFF(bDate,CURDATE())/365.25*-1) > 30 AND
    (SELECT a.*
    FROM AUTHOR a 
    WHERE (SELECT count(paperId) from AUTHOR_PAP