Help:Sources

Introduction
It is good to indicate where the information comes from. This is done in in the last of the page in a section called Sources.

Ordering
If there are multiple sources, they are to be listed first in chronological order, then alphabetically on the name of the (first) author.

As stated on Help:Page Editing, the sources should be using a bulleted list, ordered by date of (first) publication, and after that alphabetically, sorted on the surname of the (first) author.

For example (an excerpt of the Sources section of Definition:Set Union):

Types of sources
There are several templates that can be used:

Books
Template:BookReference is used to reference a specific book which will have been documented in the Books page. The idea of this is that if you have sourced the information for a page directly from a book, then it should be possible to provide the details of that book.

Example: which can be found on the page Characteristic times Ring Element is Ring Zero.
 * : $\S 4.17$: Theorem $28$

Articles
Template:Citation is used to reference a specific article in a journal. This is still under development, as the individual Journal entries still need to be worked on.

Examples of their use can be found on various Mathematicians pages, for example: which appears on the page for.

The style of this is still evolving.

Online Sources
There are templates for the following online sources. Each one has been crafted so as to produce a reference in the style requested by the online source in question.

Khan Academy
Template:Khanacademy provides a direct link to the Khan Academy.

Example: which can be found in the page Limit of Sine of X over X/Geometric Proof.

MacTutor Biography
Template:MacTutor Biography provides a direct link to a page on the http://www-history.mcs.st-andrews.ac.uk/history/index.html website.

Example:

which can be found in the page for. Note that the link presentation is taken from the page the template is invoked from.

MathWorld
Template:MathWorld provides a direct link to a page on the http://mathworld.wolfram.com/ website.

Example: which can be found in the page Area of Sector.

Metamath
Template:Metamath provides a direct link to Metamath.

Example: which can be found in the page Principle of Transfinite Recursion.

Mizar
Template:Mizar provides a direct link to Mizar.

Example: which can be found in the page Characterization of Boundary by Basis.

OEIS
Template:OEIS provides a direct link to the On-Line Encyclopedia of Integer Sequences.

Example: which can be found in the page Square Root of 2 is Irrational.

PlanetMath
Template:Planetmath provides a direct link to a page on the http://planetmath.org/ website.

Example: which can be found in the page Urysohn's Lemma.

An alternative format for the same link is:

Springer Online Encyclopedia of Mathematics
Template:SpringerOnline provides a direct link to a page on the Springer Online Encyclopedia of Mathematics.

Example: which can be found in the page Definition:Ring (Abstract Algebra).

TORI
Template:TORI provides a direct link to the TORI source site.

Example (from Definition:Tetration):

UPDATE: It is believed that this site may have closed down, as its links now 404.

Acceptability of Online Sources
NOTE: The above are currently the ONLY web resources which are to be used as general citation sources. Others may be added to the above as and when they come to our attention as being particularly useful. So feel free to challenge this assertion if you find something which appears to be a particularly rich and productive resource.

Scholarly papers which are available online may usually also be cited.

What are not generally acceptable include:
 * Lecture notes for university courses available online (because they do not stay online forever, and this causes dead links)
 * Links to pages in homework help forums
 * Discussion pages in any web forum
 * Wikipedia -- not because we don't like them, but because as they are self-proclaimed tertiary source, there is no need to do so -- we would rather go to the actual source works. See also Wikipedia:Citing Wikipedia.

Splitting sources
In some cases it is necessary to split a referenced theorem, proof or definition into multiple pages, e.g. because a theorem contains multiple statements, a proof contains in fact multiple proofs or a definition defines multiple concepts at once. If so, the source has to be referenced at every page, and its process flow is updated according to the order in which the elements appear in the source.

Also see

 * Help:Proofs
 * Help:Multiple Proofs
 * Help:Multiple Definitions
 * Help:Merging Pages