SELECT DISTINCT VE1.V FROM VE AS VE1 WHERE NOT EXISTS (SELECT * FROM VE AS VE2 WHERE VE1.V = VE2.V AND VE2.E NOT IN (SELECT VE3.E FROM VE AS VE3 WHERE VE3.V = 1)) AND EXISTS (SELECT * FROM VE AS VE4 WHERE VE4.V = 1 AND VE4.E NOT IN (SELECT VE5.E FROM VE AS VE5 WHERE VE1.V = VE5.V));