问MySQL无法使用外键创建新表

EN

CREATE TABLE grouptosite (
  groups_id BIGINT(20),
  usertogroup_groupID BIGINT(20),
usertogroup_userID BIGINT(20),
  usertosite_id INT(10),

  gts_id INT(10) AUTO_INCREMENT NOT NULL,
  PRIMARY KEY (gts_id),
index (gts_id),
index (groups_id),
  index (usertogroup_groupID), 
index (usertogroup_userID),
  index (usertosite_id), 

FOREIGN KEY (groups_id)
    REFERENCES groups(id)
    ON UPDATE CASCADE ON DELETE RESTRICT,
  FOREIGN KEY (usertogroup_groupID, usertogroup_userID)
    REFERENCES usertogroup(groupID, userID)
    ON UPDATE CASCADE ON DELETE RESTRICT,
  FOREIGN KEY (usertosite_id)
    REFERENCES usertosite(id)
    ON UPDATE CASCADE ON DELETE RESTRICT  
) ENGINE=INNODB;