【正确答案】 Two types of documents, indexes and abstracts, contain catalogs and bibliographies of original materials. Indexes include any of countless bibliographies of currently published materials, primarily articles in periodicals. Sometimes libraries have taken the initiative to create these finding aids for journal articles. For example, the U. S. National Library of Medicine has created Index Medicus, a monthly listing of current articles from some 3, 500 biomedical journals throughout the world. In other cases, scientific societies have taken the initiative. Early in the 20th century, the A-merican Chemical Society began to prepare indexes and abstracts to help chemists obtain information about the literature in their field, and the Institute of Physics in the United Kingdom took a similar responsibility for physics. The long series of indexes published by the H. W. Wilson Company of New York City and covering many different fields is well known and widely used in other counties, though their coverage is mainly limited to American publications. This has resulted in other national efforts, such as the Current Technology Index (Britain) and the British Education Index.
Bibliography (bibliograohia in Greek, " the writing of books") , originally means the writing or copying of books. Since the 18 th century, the word has come to mean a list of books or forms of written material , or the technique of compiling such a list. Certain kinds of information are supplied in a bibliography: authors , titles, editions, and dates and places of publication ; style of type, book size, and other physical characteristics may also be included. Frequently, bibliographies are annotated, that is, brief notes indicating the subject treated or commenting on the usefulness of a book are appended. Bibliographies, essential to scholars and those involved professionally with books— collectors, librarians, and dealers—can be useful sources of information for all serious readers.