並前往https://books.google.com.tw/books?id=gK0WDAAAQBAJ&pg=PA120&lpg=PA120&dq=dual&source=bl&ots=YgLa4HPGKJ&sig=ACfU3U3a4z9H6ZFdbeHEw7Tasx6CzqCJsg&hl=zh-TW&sa=X&ved=2ahUKEwjJ6_SN-Lf9AhWtl2oFHR4FAhYQ6AF6BQjzAhAD