The author-year system of documentation is used more on the undergraduate level than the graduate. Fields that have ties to the liberal arts, such as geography, human development, and political science, tend to favor the author-year system.
Your basic job when using this system is to indicate right in the text—in parentheses—the author(s) and year of publication of the reference you are citing. Since the citation becomes part of your sentence, you delay the appropriate punctuation until after the parentheses:
In recent decades, anthropogenic activities such as deforestation, desertification, and urbanization have significantly altered the land surface (Nicholson 2007).
Many writers identify the source as soon as they begin the reference, including the author’s name directly in the text and supplying only the year in parentheses:
Furlong et al. (2001) estimate that the first Mt. Erebus eruption . . .
If you use two or more articles written by the same author(s) in the same year, you distinguish between the documents in your text and on your references page by using an "a,b,c" system, providing an identifying letter after the year:
Toon (1989a) found evidence of . . .
When citing web-based sources in your text, you will often encounter sources with no author listed. Handle these cases just as you would when citing print sources—that is, if no author’s name is given in the original, offer the title of the web page, or the publication’s title, or the publisher’s name. If such a title is lengthy enough to be awkward, offer a clear shortened form of the title, with the goal of making it easy for us to find the source on the references page. In the following example, a document authored by a governmental agency is identified by a shortened form of its name:
Coordinated measurements planned in the framework of the original program should help to explain the apparent discrepancies in the data (PRIMO document, 1989).
Other In-Text Citation Practices
Slight but important mechanical differences exist among in-text citation practices, in particular when you are trying to conform to a specific style, such as MLA (Modern Language Association) or APA (American Psychological Association). For example, MLA style requires you to provide the page number of your citation in-text, but not the year, while APA style asks you to place a comma between author and year. Please feel welcome to explore all of these nuances for yourself if you wish, and recognize that some professors will insist that you conform to a particular style. When professors do not dictate a particular style, they will usually simply expect you to use the author-year or number system with consistency throughout the paper.
Remember, too, that journals within your field have already made informed decisions about which in-text citation practices they use. To settle on citation particulars, many writers model a journal in their field—mandatory, of course, if you submit material to a journal hoping for publication.
Read up on the specifics of various citation styles, in particular MLA and APA, at the following pages: