一般是在主题句之后，依次罗列段落指示词所表达的几个部分或几个方面。然后，选用丰富的事例对所罗列的各个部分或各个方面进行具体地说明或解释。
There are three basic kinds of materials that can be found in any good library.
First, there are books on all subjects, both in English and in many other languages. These books are organized according to subject, title, and author in a central file canned the card catalog. Books can generally be checked out of the library and taken home for a period of two to four weeks.
Second, there are reference works, which include encyclopedias, dictionaries, bibliography, atlases, etc., and which generally must be used in the library itself.
Third, there are periodicals- magazines, newspapers, pamphlets-which are filed
alphabetically in racks, or which have been filmed to conserve space. Like reference works, periodicals cannot usually be removed from the library. 分类时常用：most of all， next，moreover， in addition，besides，furthermore，to begin with，to start with，first of all，first，second，third?
