- As stated above, there is no shortcut for learning English grammar. (如上所述，學習英文文法沒有捷徑) (正)
- As stated before, there is no shortcut for learning English grammar. (誤)
解說：在正式寫作中，我們經常會使用到 as mentioned above (如上所述，如上面所提及的)、as noted above (如上面所指出的)、as demonstrated above (如上所示)、as shown above (如上所示) 和 as stated above (如上所述，如前所述) 等片語來表示上文、上面或之前所提到的事物，但在這些片語中，不可使用 before 來代替 above。再舉一例：
- As noted above, the government lacks efficiency. (如上面所指出的，這個政府缺乏效率) (正)
- As noted before, the government lacks efficiency. (誤)
想請問在presentation的時候是不是可以說As stated/mentioned before 接續剛剛提及的事情
ex. As (what John) mentioned before/a couple of minutes ago
可以，但必須是在同一個簡報中先前提過的。本文所講的這幾個片語，只能用在同一文件、同一本書或同一篇文章或論文。As (what John) mentioned before/a couple of minutes ago，是用來表示之前某個時間點提到的事，但 what John 不能省略。