REFERENCES clause

REFERENCES tableName [ ( simpleColumnName [ , simpleColumnName ]* ) ]
[ ON DELETE { NO ACTION | RESTRICT | CASCADE | SET NULL } ]
   [ ON UPDATE { NO ACTION | RESTRICT } ]
|
[ ON UPDATE { NO ACTION | RESTRICT } ] 
   [ ON DELETE { NO ACTION | RESTRICT | CASCADE | SET NULL } ] 
Related reference
columnLevelConstraint
tableLevelConstraint