Wikipedia:Scientific citation guidelines

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This page is a guideline for Mathematics and Physics.

It expresses the consensus of editors in those projects about specific details of inline citation. Editors in other scientific projects should follow the practice followed by those projects.

This guideline is not set in stone and should be treated with common sense and the occasional exception. When editing this page, please ensure that your revision reflects consensus. When in doubt, discuss first on the talk page.

The no original research and verifiability policies are of paramount importance to Wikipedia. Information presented in Wikipedia should be easily verifiable by anyone who wishes to do so. To ease verification, sources should be detailed by the articles. The manual of style provides advice about citing sources. Given the increasing importance that the Wikipedia community puts on footnotes and other in-line citation systems, there is a need to clarify how these guidelines should be implemented in practice. "How and where to cite sources" states:

When writing a new article or adding references to an existing article that has none, follow the established practice for the appropriate profession or discipline that the article is concerning (if available and unquestioned).

These guidelines elucidate good practice for referencing science and mathematics articles in order to achieve a reasonable balance between ease of verification, readability and editability. They also establish sensible guidelines for problems specific to Wikipedia (rather than writing for journals or a pedagogical textbook). For consistency, footnotes are used throughout. However, Harvard referencing is equally acceptable in Wikipedia.

Contents

[edit] Uncontroversial knowledge

Some statements are uncontroversial and widely known among people familiar with a discipline. Such facts may be taught in university courses, found in textbooks, or contained in multiple references in the research literature (most importantly in review articles). Some examples are:

These statements are not common knowledge, but the first should be known to anyone with an undergraduate background in physics, the second to anyone knowledgeable about condensed matter physics, and the third to anyone knowledgeable about string theory.

The verifiability criteria require that such statements be sourced so that in principle anyone can verify them. However, in many articles it is cumbersome to provide an in-line reference for every statement. In addition, such dense referencing can obscure the logical interdependence of statements. Therefore, in sections or articles that present well-known and uncontroversial information – information that is readily available in most common and obvious books on the subject – it is acceptable to give an inline citation for one or two authoritative sources at the start (and possibly a more accessible source, if one is available) in such a way as to indicate that these sources can be checked to verify later statements for which no in-line citation is provided.

For example, from aldol reaction:

The aldol reaction is an important carbon-carbon bond forming reaction in organic chemistry[1][2][3] involving the addition of an enol or enolate anion to an aldehyde or ketone.[4][5] In the aldol addition, the reaction results in a β-hydroxy ketone (or aldehyde), also called an "aldol" (aldehyde + alcohol). In the aldol condensation, the initial aldol adduct undergoes dehydration (loss of water) to form an α,β-unsaturated ketone (or aldehyde).
The enol or enolate is itself generated from a carbonyl compound, often an aldehyde or ketone, using acid or base. If the enol or enolate is formed in situ, the process can be considered as an acid or base-catalyzed reaction of one carbonyl compound with another. This may involve one aldehyde or ketone reacting with itself. Alternatively two different carbonyl compounds may be used, in which case the reaction is known as a crossed aldol reaction. In the scheme shown, the enol or enolate of a methyl ketone reacts with an aldehyde.

Five references are provided early on: two textbooks, a specialized monograph on aldol reactions, and two review articles. Most readers would assume that the bulk of the statements in the comparatively short Wikipedia article could be verified by checking any of these references, and so it may only be necessary to provide additional in-line references for controversial statements, for recent discoveries that are not covered in the standard references, for historical and academic attribution, and for verifying more specialized statements or subsections.

Wikipedia guideline WP:V states that if an editor requests that a particular statement be sourced, that request should be fulfilled. In this case, it may be advisable to add an in-line citation if this would prevent future confusion. However, if the statement is easily found in the principal references already given in the article, a citation may instead be provided on the article's associated talk page.

[edit] Attribution

Some statements require attribution. Just as it is conventional in journals to provide a reference for an idea that is not the author's own, Wikipedia's no original research policy requires that we make it clear assertions do not originate with Wikipedia's editors. Where possible, Wikipedia should strive to provide the original reference for any discovery, breakthrough, or novel theoretical development, both for attribution and historical completeness:

When the original reference is not suitable as an introduction to the idea, either because it is outdated or because it contains serious errors, it is helpful to note this in an annotation:

A related issue of attribution is eponyms:

  • ...the Michelson-Morley experiment[9]...
  • ...the Sunyaev-Zel'dovich effect[10]...
  • ...the Green-Schwarz anomaly cancellation mechanism[11]...
  • ...the αβγ neutron capture theory[12]...
  • ...the Kaluza-Klein theory of dimensional reduction[13][14][15]...

If Wikipedia has an article about an eponymous topic – such as Michelson-Morley experiment, Sunyaev-Zel'dovich effect, Green-Schwarz mechanism, Alpher-Bethe-Gamow paper and Kaluza-Klein theory – then editors of this article should, if feasible, explain why the names are attached to the result or experiment. To this end, editors of these articles should consider citing the original papers, even if they are not used as sources in writing the article. However, articles that only link to an eponymous article might not cite the original papers, depending on context. In this case, a reader looking for a reference may easily click the article link to find it.

Another important case is when providing numerical data. For example, from the neutrino article:

The strongest upper limit on the masses of neutrinos comes from cosmology: careful analysis of cosmological data, such as the cosmic microwave background radiation, galaxy surveys and the Lyman-alpha forest indicate that the sum of the neutrino masses must be less than 0.3 electron volts.[16]

This provides attribution for academic and historical purposes, and also makes it clear how readers can understand where a number comes from. This not only makes Wikipedia a more convenient resource for readers, but makes it easier to update when better data become available. When quoting widely known numbers such as the speed of light or numbers published by the Particle Data Group or in the CRC Handbook of Chemistry and Physics, a reference might only be needed in the most relevant article.

[edit] Summary style

Many articles on broad subjects, such as Albert Einstein, special relativity, big bang, and, indeed, physics and mathematics, have a series of sub-articles. In this case, the summary style may be used, in which a broad overview is given in the main article, and details can be found in subarticles. For citations, the summary style article says:

There is no need to repeat all specific references for the subtopics in the main "Summary style" article: the "Summary style" article summarizes the content of each of the subtopics, without need to give detailed references for each of them in the main article: these detailed references can be found in the subarticles. The "Summary style" article only contains the main references that apply to that article as a whole.

When adding material to a section in the summary style, however, it is important to ensure that the material is present in the sub-article with a reference. This also imposes additional burden in maintaining Wikipedia articles, as it is important to ensure that the broad article and its sub-articles remain consistent.

[edit] When not to use in-line references

There are a few cases when it is not necessary or helpful to provide in-line citations. Most commonly this is for short, technical articles which can be written using only two or three sources: a primary source and a review or textbook. These articles usually describe a simple result, or a common convention or notation and are, by their nature, unlikely to ever be expanded into longer articles. In this case, a short "References" section at the end of the article suffices. An example of this sort of article is scalar-vector-tensor decomposition.

[edit] Annotations

Since Wikipedia is not a paper encyclopedia references do not need to be as concise as they are in journals. In particular, it is always helpful to give the title of a journal article, and to give the complete name of the journal (Astrophysical Journal instead of Ap. J.). It is also helpful to provide data such as the ISBN for books, the ISSN for journals, and relevant database identifiers for papers. Examples include the DOI for articles in many areas of science, the PMID for articles in medicine and the MR number for mathematics articles. Also provide a weblink directly to the relevant database entry. For physics and mathematics, many articles are available as preprints on the arXiv, so it is helpful to provide the preprint number and a URL. For articles published before 1992, and many others, there is no arXiv preprint. Instead, consider linking to the ADS, SPIRES or MathSciNet entry, if one is available, or directly to the entry at the journal's website. The {{arxiv}} and {{MathSciNet}} templates may prove useful for creating these database links.

Moreover, when referring to one or more textbooks or reviews it can be very useful to give a brief annotation for each entry which indicates the level and comprehensiveness of the reference. In this case, it may be helpful to maintain separate "Notes" and "References" sections, with the Notes section containing the annotations and the References section the full formatted reference. For example:

In cosmology, the cosmic microwave background radiation is a form of electromagnetic radiation discovered in 1965 that fills the entire universe.[17]

It is also possible to provide annotations in other ways: by including them in the references section itself or by including everything in a footnote. If an annotation is particularly long (more than one or two sentences), it may be appropriate to merge some of the information into the main article instead of placing it in an annotation.

[edit] Examples, derivations and restatements

Wikipedia is neither a textbook nor a journal. Nonetheless, in mathematics and the mathematical sciences, it is frequently helpful to quote theorems, include simple derivations, and provide illustrative examples. For reasons of notation, clarity, consistency, or simplicity it is often necessary to state things in a slightly different way than they are stated in the references, to provide a different derivation, or to provide an original example. This is standard practice in journals, and does not make any claim of novelty.[18] In Wikipedia articles this does not constitute original research and is perfectly permissible – in fact, encouraged – provided that a reader who reads and understands the references can easily see how the material in the Wikipedia article can be inferred.

As an example, the article on the Lambda-CDM model quotes values for Hubble parameter h and the fraction of the present universe made up of baryons, Ωb. For technical reasons having to do with their Fisher matrix, the WMAP collaboration quotes values for h and Ωbh2.[19] The values quoted in the article are more useful for the lay reader. Any reader who looks at the WMAP paper, and has a basic knowledge of error analyses, will understand how to go from one to the other.

[edit] Notes

  1. ^ Wade, L. G. Organic Chemistry, 6th ed., Prentice Hall, Upper Saddle River, New Jersey, 2005; pp 1056-1066. ISBN 013187151
  2. ^ Smith, M. B.; March, J. Advanced Organic Chemistry, 5th ed., Wiley Interscience, New York, 2001; pp 1218-1223. ISBN 0-471-58589-0
  3. ^ Mahrwald, R. (ed.) Modern Aldol Reactions, Volumes 1 and 2, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2004. ISBN 3-527-30714-1.
  4. ^ Heathcock, C. H. (1991), "The aldol reaction", in Comprehensive Organic Synthesis, B. M. Trost and I. Fleming (Eds.), Pergamon Press, Oxford, 1991; vol. 2, pp. 133–179. (Review)
  5. ^ Mukaiyama, T., "The directed aldol reaction", in Organic Reactions, John Wiley & Sons, New York, 1982; vol. 28, pp. 203–331. (Review)
  6. ^ IAUC4316: 1987A, N. Cen. 1986 (24 February 1987).
  7. ^ Michel A. Kervaire; John W. Milnor. "Groups of Homotopy Spheres: I" in The Annals of Mathematics, 2nd Ser., Vol. 77, No. 3. (May, 1963), pp. 504-537. This paper calculates the structure of the group of smooth structures on an n-sphere for n > 4.
  8. ^ Slipher first reports on his measurement in the inaugural volume of the Lowell Observatory Bulletin, pp.2.56-2.57[1]. His article entitled The radial velocity of the Andromeda Nebula reports making the first Doppler measurement on September 17, 1912. In his report Slipher writes: "The magnitude of this velocity, which is the greatest hitherto observed, raises the question whether the velocity-like displacement might not be due to some other cause, but I believe we have at present no other interpretation for it." Three years later, in the journal Popular Astronomy, Vol. 23, p. 21-24 [2], Slipher wrote a review entitled Spectrographic Observations of Nebulae. In it he states, "The early discovery that the great Andromeda spiral had the quite exceptional velocity of - 300 km(/s) showed the means then available, capable of investigating not only the spectra of the spirals but their velocities as well." Slipher reported the velocities for 15 spiral nebulae spread across the entire celestial sphere, all but three having observable "positive" (that is recessional) velocities.
  9. ^ A. A. Michelson and E.W. Morley, Philos. Mag. S.5, 24 (151), 449-463 (1887)
  10. ^ Sunyaev, R. A., Ya. B. Zel'dovich (1970). "Small-Scale Fluctuations of Relic Radiation". Astrophysics and Space Science 7: 3.
  11. ^ Michael B. Green, John H. Schwarz, "Anomaly Cancellation in Supersymmetric D=10 Gauge Theory and Superstring Theory", Physics Letters B149 (1984) pp. 117–22.
  12. ^ R. A. Alpher, H. A. Bethe, G. Gamow, "The Origin of Chemical Elements,"Physical Review 73 (1948), 803.
  13. ^ Gunnar Nordström, Uber die Möglichkeit, das elektromagnetische Feld und das Gravitationsfeld zu vereinigen (On the possibility of a unification of the electromagnetic and gravitational fields), Physik. Zeitschr. 15 504-506 (1914).
  14. ^ Theodor Kaluza, On the problem of unity in physics, Sitzungsber. Preuss. Akad. Wiss. Berlin. (Math. Phys.) 966-972 (1921).
  15. ^ Oskar Klein, Quantum theory and five dimensional theory of relativity, Z. Phys. 37 895-906 (1926).
  16. ^ A. Goobar, S. Hannestad, E. Mörtsell and H. Tu (2006). "A new bound on the neutrino mass from the SDSS baryon acoustic peak". JCAP 06: 019. arXiv:astro-ph/0602155
  17. ^ Dodelson (2003) is a modern textbook which contains a comprehensive derivation of cosmic microwave background physics. Liddle and Lyth (2000) and Mukhanov (2005) are other modern textbooks. Kolb and Turner (1988) is a dated but classic textbook. Peebles (1993) gives a comprehensive overview of cosmology and useful remarks and references for the history of cosmic microwave background physics. Hu and Dodelson (2002) is a recent review. Wayne Hu's website contains a variety of useful introductory material targeted at different levels.
  18. ^ See Manifold Destiny for a possible counterexample.
  19. ^ D. N. Spergel et al. (WMAP collaboration) (March 2006). "Wilkinson Microwave Anisotropy Probe (WMAP) three year results: implications for cosmology".

[edit] References

[edit] See also

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