He said [that he had invited Medvedev to visit the United States in June and that he hoped the trip would showcase steps (which) the United States and Russia are taking to strengthen economic ties between the two nations]... E thêm which vào chị đã hiểu rõ cấu trúc chưa ạ!?? Chủ ngữ của are taking là The USA và R, chứ k fai That ạ. Sorry vì nãy e bận nghe dt nên k để ý.