重点讲解：
1. reference to
提及；谈到；有关；
eg. He made no reference to any agreement.
他没有提到什么协议。
eg. I am writing with reference to your job application.
敬覆者，关于您申请工作一事。
2. come from
来自；始于；
eg. Nearly half the students come from abroad.
将近一半的学生来自国外。
eg. Chocolate comes from the cacao tree.
巧克力出自可可树。
eg. The term 'claret', used to describe Bordeaux wines, may come from the French word 'clairet'.
用来指称波尔多葡萄酒的词 claret 可能源于法语单词 clairet。
3. stand for
代表，表示；
eg. What does EU stand for?
EU代表什么？
eg. The letter "x" is often used to stand for an unknown number.
字母x常被用来代表一个未知数。