When you have used information from an external source, you are responsible for giving credit to that source.  There are several different systems that can be used to acknowledge those sources.  Each one is similar in that the purpose is to clearly identify to your reader the specific source from which you borrowed.  Each is different in the format used, what information is emphasized, and where the information is presented in your finished paper.
     The Central Bucks English Department has adopted the form that is used in literature papers (at all academic levels) and that is also most commonly taught in high school textbooks for all subject areas.  That format is a name and page system called in-text citation, following the MLA (Modern Language Association, 4th edition, 1995).   In in-text MLA citation, you list the author and the page number in parentheses right in the body of the paper.
     Some subject areas, especially at the college and graduate school level, use a different format.  The social sciences (including anthropology, psychology, and sociology), biology, and earth sciences are among the disciplines using another type of in-text citation, a name and year system.  The most well-known example of that format is APA (American Psychological Association).  In in-text APA citation, you list the author and year in parentheses right in the body of the paper.
      The applied sciences and mathematics sometimes use a number system in which each reference book is given a number.  Any time that source is referred to, just the number of the book is listed in parentheses in the body of the paper.
     A few disciplines, specifically the fine arts and history, use another form of citation, which has diminished in popularity in recent years.  That is the footnote / endnote system, in which a superscript number follows a citation in the text and all of the information about that source (author, title, publisher, copyright, page referenced) is located on the bottom of the page (footnote) or at the end of the paper (endnote).  The most well known footnote format is the Chicago Manual of Style, 13th edition, 1982.
     If your teacher specifies a form other than MLA in-text citation, follow his / her instructions.
     The MLA in-text citation format states as a general rule that you must provide just enough information within the text of the paper to locate a source, which will have full details explained on the Works Cited page.  The in-text information in the body of your paper must match the information in the entry on the Works Cited page.  The following section will help you to correctly use in-text citation from a number of different sources.