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Referencing styles - a Practical Guide

APA

American Psychological Association (APA) referencing style

Used by: Education, Language & Linguistic Science, Psychology

Introduction to APA referencing style

The American Psychological Association (APA) style is used in psychology, health and the social sciences. This guide is gradually being updated to APA Style 7th edition. We've noted where the section is updated but otherwise assume the guidance is for APA 6th. Check your department requirements for which version to use.

In-text citations

Information from sources in the text is shown with in-text citations that include the author's surname and the publication year (and a page number in some situations). These can appear after the information, or integrated into the sentence:

Passive tutorials (Anderson & Wilson, 2009) or text-based resources (Sachs et al., 2013) can be as effective as interactive resources.
Parramore (2019) discusses online active learning in more depth...

The in-text citation examples given throughout this guide use the (Neville, 2010) version.

Reference list

The reference list at the end of the document includes the full details of each source so the reader can find them themselves. The list is organised alphabetically by author surname. 

The information to include depends on the types of source - see the examples on this page.

Useful resources

Guidance for all source types

This guidance applies to all source types.

1 author

In-text: (Santrock, 2011)

Reference List:

Santrock, J. W. (2011). Child development. McGraw-Hill.

2 authors

List both authors in the order they appear in the publication. Use an ampersand (&), not 'and' between names.

In-text: (Lee & Benati, 2007)

Reference List:

Lee, J. F., & Benati, A. G. (2007). Second language processing: An analysis of theory, problems and possible solutions. Continuum.

3-20 authors

In the citation use the surname of the first author followed by 'et al.' (including the full stop). In the reference list, list all authors in the order they appear in the publication. Use an ampersand (&), not 'and' between names. In subsequent citations, give the first author's name followed by et al. (the full stop is important!).

In-text (Wilkinson et al., 2011)

Reference List:

Wilkinson, A., Meares, K., & Freeston, M. (2011). CBT for worry and generalised anxiety disorder. Thousand Oaks: Sage Publications.

21+ authors

In all in-text citations, give the first author's name followed by et al. (the full stop is important!). In the reference list, include the names of the first 19 authors, insert an ellipsis (three dots) but no ampersand, then include the name of the final author.

In-text: (Halonen, et al., 2003)

Reference List:

Halonen, J. S., Bosack, T., Clay, S. McCarthy, M., Dunn, D. S., Hill, G.W.,IV, … Whitlock, K. (2003). A rubric for learning, teaching, and assessing scientific inquiry in psychology. Teaching of Psychology, 30(3), 196-208.

If you're pulling together information from a number of sources to support your argument you may want to include more than one source in one in-text citation. For example:

As is widely stated in the literature... (Carroll, 2002; Mallon,1991; Neville, 2010).

They should appear alphabetically, matching the order in which they will appear in your reference list.

If an author (or a group of authors) have more than one publications in the same year, add lower-case letters (a, b, c, etc.) to the year to differentiate between them. Add a to the first source cited, b to the second course and so on.  For example:

In-text: (Carroll, 2007a; Carroll, 2007b)

References:

Carroll, J. (2007a). A handbook for deterring plagiarism in higher education. Oxford: Oxford Centre for Staff and Learning Development, Oxford Brookes University.
Carroll, J. (2007b). Do national statistics about plagiarism tell you about your students? LINK Newsletter on Academic Integrity. The Hospitality, Sport and Leisure Subject Centre, 18, 3-9.

No author name

It's important to use quality sources to support your arguments, so you should carefully consider the value of using any source when you can't identify its author. 

For online sources, look carefully for named contributors, such as in the ‘about us’ sections. For printed material look carefully at the publication/ copyright information, which is often on the inside cover of a book or back page of a report. If you cannot locate the information you could use the name of the organisation for the author, for example (NSPCC, 2012).

No publication date

Knowing when a source was created, published, or last updated is important as this helps you to determine the relevance and reliability of the source. For online sources look carefully for created and/ or last updated dates on the page(s). If you can't locate a date write (n.d.) instead of the year to denote ‘no date’.

Quotations are word-for-word text included in your work and must be clearly distinguished from your own words and ideas. You must also include the page number(s) in the in-text citation.

Short quotations (less than 40 words)

Use a brief-phrase within your paragraph or sentence to introduce the quotation before including it inside double quotation marks “ ”.  For example:

As Neville (2010) states, “you should cite all sources and present full details of these in your list of references” (p.37).

Longer quotations (40 words or more)

Use block quotation, without quotation marks, but clearly indented to indicate these words are not your own. For example:

Neville (2010) comments that:
It can sometimes be difficult, if not impossible, to avoid using some of the author’s original words, particularly those that describe or label phenomena. However, you need to avoid copying out what the author said, word for word. Choose words that you feel give a true impression of the author’s original ideas or action (p.38).

A secondary reference is given when you are referring to a source which you have not read yourself, but have read about in another source, for example referring to Jones’ work that you have read about in Smith. Avoid using secondary references wherever possible and locate the original source and reference that.

Only give a secondary reference where it's not possible to read the original source, and you think it's essential to use the material. It is important to think carefully about using secondary references as the explanation or interpretation of that source by the author you have read may not be accurate. For example, if Allport's work is cited in Nicholson and you did not read Allport's work, list the Nicholson reference in the reference list. In the text, use the following citation:

Allport's diary (as cited in Nicholson, 2003).

Only list the sources that you have read in your reference list - ie. list Nicholson but not Allport in the reference list.

Include the page number(s) in an in-text citation when:

  • quoting directly
  • referring to a specific detail in a text (eg, a specific theory or idea, an illustration, a table, a set of statistics).

Giving page numbers lets the reader locate the specific item you're referring to.

You should only capitalise the first letter of the first word of a book, journal article, etc and any word following a colon in the title. The exception is if these include proper nouns – names of people or organisations.

Usually in-text citations are included in your word count as they are integral to your argument.

This may vary depending on the assignment you are writing and you should confirm this with your module tutor. If in-text citations are included this does not mean you should leave out citations where they are appropriate.

Questions about referencing?

Contact your Academic Liaison Librarian if you have any questions about referencing.

Commonly used sources (updated to APA 7th)

Examples of in-text citations and reference list entries for key source types.

Use these examples alongside the information given in the 'Guidance for all source types' box. Pay particular attention to the guidance on formatting for one, two or more authors.

In-text: (Santrock, 2011)

Reference list:

Information to include
Author(s) Surname, Initial. (year). Name of book (Edition if not the first). Publisher name. Doi if available

Santrock, J. W. (2011). Child development (13th ed.). McGraw-Hill.

For books written or published in another language, see the Book (translated to English) and Book (read in another language) sections below.

Chapter in an edited book

In-text: (Alexander, 2009)

Reference list:

Information to include
Chapter author(s) Surname, Initial. (year). Title of chapter. In editor(s) Initial, Surname (Ed/Eds.), Title of edited book. (pp. Page numbers). Publisher name. Doi if available

Alexander, R. J. (2009). Pedagogy, culture and the power of comparison. In H. Daniels, H. Lauder, & J. Porter (Eds.), Educational theories, cultures and learning: A critical perspective (pp. 10-26). Routledge. https://doi.org/10.4324/9780203379417

 

Edited book as a whole

In-text: (Daniels et al., 2009)

Reference list:

Information to include
Editor(s) Surname, Initial. (Ed/Eds.). (year). Title of edited book. Publisher name. Doi if available

Daniels, H., Lauder, H., & Porter, J. (Eds.). (2009). Educational theories, cultures and learning: A critical perspective. Routledge. https://doi.org/10.4324/9780203379417

Most journal papers are now available in electronic form, usually with a DOI (a special type of link). If there isn't a DOI, include the URL instead or leave this out if you are referencing a printed journal article.

In-text: (Forlin, 2010)

Reference list:

Information to include
Author(s) Surname, Initial. (year). Title of paper. Name of journal. volume(issue). page numbers. DOI if available

Forlin, C. (2010). Developing and implementing quality inclusive education in Hong Kong: Implications for teacher education. Journal of Research in Special Educational Needs, 10(issue supplement s1), 177-184. https://doi.org/10.1111/j.1471-3802.2010.01162.x

Newspaper/magazine article

Include the most precise date of publication given - usually full date for newspaper articles, month and year for magazines.

In-text: (Clarkson, 2008; Swain, 2008)

Reference list:

Information needed
Author(s) Surname, Initial. (year, month date). Title of article. Name of newspaper/magazine. p. page numbers.

Clarkson, S. (2008, December). Wanted: 25 hours in the day. Red Magazine, p. 91-94.
Swain, H. (2008, September 23). The art of doing an assessed assignment. The Guardian: Education supplement, p. 11.

 

Newspaper/magazine article (without named author)

Use the article title instead of the author name. In the in-text citation, put the title (or a shortened version) between quotation marks (").

In-text: ("Editorial: French Elections," 2012)

Reference list:

Information needed
Title of article. (year, month date). Name of newspaper/magazine. p. page numbers.

Editorial: French elections. Bitter-sweet victory for the left. (2012 April 23). The Guardian, p. 26.

Website with author

In-text: (Richardson, 2011)

Reference List:

Information to include
Author(s) Surname, Initial. (year). Name of specific webpage. Name of full website. URL

Richardson, H. (2011). Schools 'pushed into phonics by financial incentives. BBC News. http://www.bbc.co.uk/news/education-14029897

Website without named author

In-text: (BBC News, 2011)

Reference list:

Information to include
Name of full website (year). Name of specific webpage.  URL

BBC News. (2011). University changes: Threat or opportunity? http://www.bbc.co.uk/news/education-13951020

Further sources

Examples of in-text citations and reference list entries for other source types.

Use these examples alongside the information given in the 'Guidance for all source types' box. Pay particular attention to the guidance on formatting for one, two or more authors.

In-text: (Education Act 2011)

Reference list:

Education Act 2011, ch. 21.

In-text: (Master Atlas of Greater London, 2007)

Reference List:

Master atlas of Greater London (11th ed.). (2007). Sevenoaks: Geographers' A-Z Map Company.

In-text: (Brandon, 2010)

Reference List:

G Brandon (2010, November 20). Stress and education. [Blog post]. Retrieved July 24, 2012 from http://www.psychblog.co.uk/stress-and- education-967.html

If you are reading an English language version of a book originally published in another language follow this example.

In-text: (Freud, 2002)
Bibliography/ Reference List:

Freud, S. (2002). The psychopathology of everyday life (A. Bell, Trans.). London: Penguin. (Original work published 1901)

If you are reading a book in another language, follow this example:

In-text: (Hoops, 1932)

Bibliography/ Reference List:

Hoops, J. (1932). Kommentar zum Beowulf. [Commentary on Beowulf]. Hiedelberg: Carl Winters Universitatsbuchhandlung.

In-text: (The Cogent Group, 2009)

Reference list:

The Cogent Group. (2009). COGENT (Version 2.3) [Computer software]. London: The Cogent Group, Birkbeck University of London. Retrieved July 24, 2012 from http://cogent.psyc.bbk.ac.uk/

Conference paper

If conference proceedings have been published in book form, cite the paper as if for a chapter in a book.

In-text: (Bartram, 2010)

Reference list:

Bartram, D. (2010, July). When is assessment a ‘psychological act’? Unpublished paper presented at the International Test Commission Conference, Chinese University of Hong Kong, Hong Kong.

 

Full conference proceedings

If conference proceedings have been published in book form cite them as for a book.

In-text: (ALT-C, 2011)

Reference list:

ALT-C 2011. (2011). Thriving in a colder and more challenging climate. The 18th annual conference of the Association for Learning Technology (ALT-C 2011), Leeds: University of Leeds.

Include the type of resource in square brackets after its name: [CD], [CD-Rom, [DVD]

In-text: (Wedding & Stevens, 2008)

Reference list:

Wedding, D. & Stevens, M. J. (2008). Psychology: IUPsyS global resource [CD-Rom]. Hove: Psychology Press.

In-text: (Beauty and the Beast, 2012)

Reference list:

Beauty and the Beast (2012) [Ballet]. Nixon, D. (Choreographer). Leeds: Northern Ballet.

Online database (specific content)

In-text: (The National Autistic Society, n.d.)

Reference list:

The National Autistic Society. (n.d.). Employment: Tips for interviewing people with autism and Asperger syndrome. Autism Data [Electronic database]. The National Autistic Society. Retrieved July 24, 2012 from http://www.autism.org.uk/15692

Online database (as a whole)

In-text: (The National Autistic Society, n.d.)

Reference list:

The National Autistic Society. (n.d.). Autism data [Electronic database]. The National Autistic Society. Retrieved July 24, 2012 from http://www.autism.org.uk/autismdata

n.d. denotes no date given - include the year when known

In-text: (Paperback Oxford English Dictionary, 2006)

Reference list:

Paperback Oxford English Dictionary. (2006). Oxford: Oxford University Press.

If there are no page numbers, give the chapter number for direct quotes eg, "…" (Bartram, 2010, ch.1).

E-book (online)

In-text: (Bartram, 2010)

Reference list:

Bartram, B. (2010). Attitudes to modern foreign language learning: Insights from comparative education [e-book]. London: Continuum International Publishing Group. Retrieved July 24, 2012 from http://lib.myilibrary.com/Open.aspx?id=280647&src=0

E-book (using e-reader device)

In-text: (Collins, 2011)

Reference list:

Collins, N. (2011). The hunger games [Kindle]. Retrieved July 24, 2012 from http://www.amazon.co.uk/gp/product/B005EGXTEE/ref=s9_simh_gw_p351_d2_g351_i4?
  pf_rd_m=A3P5ROKL5A1OLE&pf_rd_s=center-2&pf_rd_r=0V3C55RJ3DB412MK834J&pf_rd_t=
  101&pf_rd_p=467128533&pf_rd_i=468294

Personal communications such as personal emails, private letters, and telephone conversations are non-recoverable and so are not included in the reference list. Cite them in-text only with the initials and surname of the author.

In-text: in an email from I. Johnson (personal communication, 22 May 2012)

Note: No personal communication is included in your reference list; instead, parenthetically cite the communicator's name, the phrase "personal communication," and the date of the communication in your main text only.

Encyclopedia as a whole

In-text: (Hornberger, 2008)

Reference list:

Hornberger, N. H. (2008). Encyclopedia of language and education. New York: Springer.

Encyclopedia (specific entry)

In-text: (Manstead & Hewston, 1996)

Reference list:

Manstead, T., & Hewston, M. (1996). Empathy/sympathy and altruistic motivation. In The Blackwell encyclopaedia of social psychology (p. 205). Malden: Wiley-Blackwell.

In-text: (Lloyd, 2008)

Reference list:

Lloyd, P. (Director). (2008). Mamma Mia [Film]. London: Universal Pictures UK.

In-text: (Great Britain. Dept. for Education, 2010)

Reference list:

Great Britain. Dept for Education. (2010). The importance of teaching. (Cm. 7980). London: The Stationery Office.

Cm. is the abbreviation used to designate a command paper. This example is command paper 7980.

Print copy, with figure number

In-text: [INSERT IMAGE] Table X Common Abbreviations for Units of Measurement (APA, 2010, p. 109, table 4.4)

Reference List:

APA. (2010). Publication manual of the American Psychological Association (6th ed.) Washington DC: APA.

Online, no figure number

In-text: [INSERT IMAGE] Classical Conditioning (Kulich, 2006)

Reference list:

Kulich, R. J. (2006). Classical conditioning. Retrieved July 24, 2012 from http://ocw.tufts.edu/Content/24/lecturenotes/329811/329819

Conducted by someone else

Eg, an interview conducted by someone else that has been published in such as a newspaper or journal

In-text: (Beard, 2012)

Reference list:

Beard, M. (2012). A Roman holiday with Cicero (and Mr Hot Sex, too). Interview with M. Reisz. Times Higher Education, 19 April 2012, pp.48-49.

Conducted yourself

You are not encouraged to cite these, except where an interview has been conducted as part of a non-empirical assignment. That is, only cite if you discuss an interview within your assignment where you had not been required to conduct interviews, but did so to augment your work. Consideration also needs to be given to confidentiality and interviewee anonymity as appropriate.

In-text: (Smith, 2012)

Reference list:

Smith, J. (2012, March 2). Personal interview. Staff recruitment survey for MA project. At Bright Sparks, York, with Jim Doe (see appendix item 1).

In-text: (Andrews, 2010)

Reference list:

Andrews, T. (2010, October 26). Introduction to psychology as a biological science. Introduction to Psychology as a Biological Science module. BSc Psychology year 2. York: University of York.

In-text: (Andrews, 2010)

Reference list:

Andrews, T. (2010). Introduction to psychology as a biological science. Introduction to psychology as a biological science module lecture notes. University of York: Department of Psychology.

Personal communications such as personal emails, private letters, and telephone conversations are non-recoverable and so are not included in the reference list. Cite them in-text only with the initials and surname of the author.

In-text: Johnson, I. (2011, August 4). Letter to the author.

Bibliography/ Reference List:

 If the letter is published: 

Berkowitz, A. D. (2000, November 24). How to tackle the problem of student drinking [Letter to the editor]. The Chronicle of Higher Education, p. 20.

If the letter is from an unpublished collection: 

Sullivan, Harold. (March 28, 1940). Letter from Harold Sullivan to Dorothy Day (Series W-4, Box 2). Dorothy Day-Catholic Worker Collection, Department of Special Collections and University Archives, Marquette University, Milwaukee, WI.

In-text: (Munshi, 2010)

Reference list:

Munshi, S. (2010) Transcription: Monologue on the history of polo. University of North Texas Libraries, UNT Digital Library. Retrieved March 18, 2022 from https://digital.library.unt.edu/ark:/67531/metadc967341/

In-text: (Cotton MS Caligula A IX, 1250-1300)

Reference list:

Cotton MS Caligula A IX (1250-1300). British Library, Digitised Manuscripts. Retrieved 18 March 2022 from http://www.bl.uk/manuscripts/FullDisplay.aspx?ref=Cotton_MS_Caligula_A_IX

Each one will have titles and references within it or you can refer to the actual microfiche record number, where it is stored and when accessed. This is an example of a historic periodical.

In-text: In-text: (Brown, 1794)

Reference list:

Brown, J. (1794). Freemason’s magazine [microfiche]. London: Early English Newspaper series.

In-text: (Vitebsk, 2012)

Reference list:

Vitebsk. Copland, A. (2012, January 18). Sasaki Trio. York: Sir Jack Lyons Concert Hall.

In-text: (Puccini, 1980)

Reference list:

Puccini, G. (1980). Tosca. Edited by Mario Parenti. Milan: Ricardi.

In-text: (YaleCourses, 2008)

Reference list:

YaleCourses. (2008, September 30). Introduction to psychology [Online video]. Retrieved July 11, 2011 from http://www.youtube.com/watch?v=rCKK6r15fro&playnext=1&list=PL6A08EB4EEFF3E91F

In-text: (Monet, 1899)

Reference list:

Monet, C. (1899). The water-lily pond [Painting]. London: National Gallery.

In-text: first citation (Gardner, Harlen, Hayward, & Stobart, 2008), subsequent citations Gardner et al., 2008)

Reference list:

Gardner, J., Harlen, W., Hayward, L., & Stobart, G. (2008). Changing assessment practice. Process, principles and standards. Belfast: Assessment Reform Group.

In-text:(Higher Education (Fees) Bill HL 2012-13)

Reference list:

Higher Education (Fees) Bill HL 2012-13 [22]. London: The Stationery Office.

 

HC stands for House of Commons, with HL being used for Bills originating in the House of Lords. The date represents the parliamentary session and the number in [ ] the number of the bill.

In-text: (U.S. Patent No. D582022, 2008)

Reference list:

Berberet, S., & Bates, M. (2008). US Patent No. D582022. Washington, DC: US Patent and Trademark Office.

 

OR

In-text: (Berberet & Bates, Kohler Company, 2008)

Reference list:

Berberet, S., & Bates, M. (2008). Fitting for plumbing fixture. US Patent D582022. Appl. 2 December 2008.

In-text: (Jarche, 1931)

Reference list:

Jarche, J. (1931). Miner with pit pony [Photograph]. Bradford: National Media Museum.

In-text: (Yes, Prime Minister, 2012)

Reference list:

Yes, Prime Minister by Lynn, J. (2012, April 16) [Play]. Theatre Royal, York. Performers: Graham Seed and Michael Simkins. Director: Jonathan Lynn.

In-text: (Webster, 1998)

Reference list:

Webster, J. (1998). The white devil. Oxford: Oxford University Press.

In-text: (Kipling, 1999, p. 530)

Reference list:

Kipling, R. (1999). The story of Uriah. In C. Ricks (Ed.), The Oxford book of English verse (p. 530). Oxford: Oxford University Press.

In-text: (Teachers TV, 2008)

Reference list:

Teachers TV (Producer). (2008). Understanding autism [Audio Podcast]. Retrieved July 24, 2012 from http://www.guardian.co.uk/education/video/2008/nov/18/understanding-autism-teachers-tv

In-text: (O'Dea, 2011)

Reference list:

O'Dea, B. (Producer). (2011, July 19). A good read. London: BBC Radio 4.

Religious and sacred texts include such as the Bible, Talmud, and Qur’an.

The Publication Manual of the APA (2010, p.179) states that you do not need to include religious or sacred texts in the reference list. Identify the version of the text used in the first citation and provide the book, chapter, and verse details in a universally accepted, consistent form.

For example:
1 Cor. 13:1 (Revised Standard Version).
This refers to St Paul’s 1st letter to the Corinthians, chapter 13, verse 1 sourced from the Revised Standard Version of the Bible.
(Qur’an 5:3-4).
This refers to chapter 5, verses 3-4 of the Qur’an.

Report (online)

In-text: (Hollingworth & Mansaray, 2012)

Reference list:

Hollingworth, S., & Mansaray, A. (2012). Language diversity and attainment in English secondary schools: A scoping study. Retrieved July 24, 2012 from The Institute for Policy Studies in Education, London Metropolitan University: http://www.londonmet.ac.uk/fms/MRSite/Research/ipse/Language/Diversity/&/Attainment/Report/2012.pdf

Report (hard copy)

In-text: (Higher Education Academy, 2008)

Reference list:

Higher Education Academy (2008). Ethnicity, gender and degree attainment project: final report. York: Higher Education Academy/ Equality Challenge Unit.

This format is for when you read a more recent version of an older work. In-text, the date of the original publication is given before the later one you read. In the bibliography/ reference list you give the date of the version you read with the original date at the end of the reference.

In-text: (Erikson, 1951/1977)

Reference list:

Erikson, E. H. (1977). Childhood and society. St Albans: Triad/Paladin.(Original work published 1951).

In-text: (Runciman, 2002)

Reference list:

Runciman, W. G. (2002). Why are we here? [Review of the book Religion explained: The human instincts that fashion gods, spirits and ancestors]. London Review of Books, 24(3), 23-24.

In-text: Belle & Sebastian, 2003, track 8)

Reference list:

Belle & Sebastian. (2003). Wrapped up in books. On Dear catastrophe waitress [CD]. London: Rough Trade Records.

In-text: (British Standards Institute, 2006)

Reference list:

British Standards Institute. (2006). BSEN14975: Loft Ladders: Requirements, marking and testing. London: British Standards Institute.

In-text: (The Apprentice, 2012)

Reference List:

The Apprentice (2012, May 23). Episode: Discount dealing. BBC1 Television.

Personal communications such as personal emails, private letters, and telephone conversations are non-recoverable and so are not included in the reference list. Cite them in-text only with the initials and surname of the author.

In-text: in a text message from I. Johnson (personal communication, 22 May 2012).

In-text: (Missuno, 2012)

Reference List:

Information to include
Author(s) Surname, Initial. (year). Title of thesis. [level of qualification, institution]. Database name.

Missuno, Filip. (2012). 'Shadow' and paradoxes of darkness in Old English and Old Norse poetic language. [Doctoral dissertation, University of York]. White Rose eTheses Online.

Use either the proper name of the author or Twitter pseudonym. In the following example either (York Psychology, 2012) or (@YorkPsychology, 2012) can be used in-text and in the Reference list reference.

In-text: (York Psychology, 2012)

Reference list:

York Psychology (2012, May 9). Neural networks predict reoffending: http://www.york.ac.uk/psychology/news-and-events/news/2012/phdforneuralnetworkpredictsreoffending/DominicPearson's PhD may have applications in assessing risk posed by prisoners [Twitter post]. Retrieved July 24, 2012 from http://twitter.com/#!/YorkPsychology/

In-text: (ELDT, 2012)

Reference list:

ELDT. (2012). Blogs in Yorkshare: An overview [Help guide]. University of York. Retrieved July 24, 2012 from Yorkshare from https://vle.york.ac.uk/bbcswebdav/institution/E-Learning/Development/Team/Guides/Bb/Blog/--/Overview.html

In-text: (Psychology Wiki, n.d.)

Reference list:

Psychology Wiki. (n.d.). Psychometrics wiki. Retrieved July 11, 2011 from http://psychology.wikia.com/wiki/Psychometrics