These are AIDS to finding articles on any subject. They list subjectheading, with various titles of articles under them, together with the location of each article.
The Email object contains properties such as the sender's address, the recipient's address, a subjectheading, and a message body, as shown in Listing 5.
如清单 5 所示， Email 对象包含了诸如发件人地址、收件人地址、主题栏和消息正文等属性。
3
They list subjectheading, with various titles of articles under them, together with the location of each article.