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 called the card catalog.  Books can generally be checked

out of the library and taken home for a period of two or four weeks. Second, there are reference works,

which include encyclopedia, bibliographies, atlases, and so forth, 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 microfilmed to conserve space. Like reference works,

periodicals usually cannot be removed from the library. In conclusion, big libraries have a variety of books.

TS: There are three basic kinds of materials that can be found in any good library

Support₁     books on all subjects.

Support₂     reference books

Support₃     periodicals

RTS: Big libraries have a variety of books.