Parenthetical referencing is a citation system in which in-text citations are made using parentheses. They are usually accompanied by a full, alphabetized list of citations in an end section, usually titled "references", "reference list", "works cited", or "end-text citations". Parenthetical referencing can be used in lieu of footnote citations (the Vancouver system).
Parenthetical referencing normally uses one of these two citation styles: Author–date (also known as Harvard referencing): primarily used in the natural sciences and social sciences, and recommended by the American Chemical Society and the American Psychological Association (APA) (see APA style); Author–title or author–page: primarily used in the arts and the humanities, and recommended by the Modern Language Association (MLA) (see MLA Handbook).
Author–date (Harvard referencing) In the author–date method (Harvard referencing), the in-text citation is placed in parentheses after the sentence or part thereof that the citation supports. The citation includes the author's name, year of publication, and page number(s) when a specific part of the source is referred to (Smith 2008, p. 1) or (Smith 2008:1). A full citation is given in the references section: Smith, John (2008). Name of Book. Name of Publisher.
How to cite
The structure of a citation under the author–date method is the author's surname, year of publication, and page number or range, in parentheses, as in "(Smith 2010, p. 1)". The page number or page range may be omitted if the entire work is cited, as in "(Smith 2010)". Narrative style citations have the author appearing as part of the regular text sentence, outside parentheses, as in: "Jones (2001) revolutionized the field of trauma surgery." Two authors are cited using "and" or "&": (Deane and Jones 1991) or (Deane & Jones 1991). More than two authors are cited using "et al.": (Smith et al. 1992). In some documentation systems (e.g., MLA style), an unknown date is cited as having "no date of publication" by the abbreviation for "no date" (Deane, n.d.). In such documentation systems, works without pagination are referred to in the References list as "not paginated" with the abbreviation for that phrase (n. pag.). "No place of publication" and/or "no publisher" are both designated the same way (n.p.) and placed in the appropriate spot in the bibliographical citation (Harvard Referencing. N.p.). A reference to a republished work is cited with the original publication date either in square brackets (Marx [1867] 1967, p. 90) or separated with a slash (Marx, 1867/1967, p. 90). The inclusion of the original publication year qualifies the suggestion otherwise that the publication originally occurred in 1967. If an author published several books in 2005, the year of the first publication (in the alphabetic order of the references) is cited and referenced as 2005a, the second as 2005b and so on. A citation is placed wherever appropriate in or after the sentence. If it is at the end of a sentence, it is placed before the period, but a citation for an entire block quote immediately follows the period at the end of the block since the citation is not an actual part of the quotation itself. When citing quotes its advisable to insert the page number as this points directly to the page the content that has been used. Complete citations are provided in alphabetical order in a section following the text, usually designated as "Works cited" or "References." The difference between a "works cited" or "references" list and a bibliography is that a bibliography may include works not directly cited in the text. All citations are in the same font as the main text. There is no official guide to Harvard citation style, consequently variations occur across various online Harvard citation and referencing guides. For example, some universities instruct students to type a book's publication date without parentheses in the reference list.
Examples
An example of a journal reference:
Heilman, J. M. and West, A. G. (2015). "Wikipedia and Medicine: Quantifying Readership, Editors, and the Significance of Natural Language." Journal of Medical Internet Research, 17(3), p. e62. doi:10.2196/jmir.4069.
Following is an explanation of the components, where the coloring is for demonstration purposes and is not used in actual formatting: