# Help:Editing/House Style/Sources

## Citations

It is good to indicate where the information comes from. This is done in $\mathsf{Pr} \infty \mathsf{fWiki}$ in the last of the page in a section called Sources.

## Adding sources

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 publication of the edition cited, and after that alphabetically, sorted on the surname of the (first) author.

- Important

When referencing a specific entry in that work, please do not use the page number of the work, as reprints and re-issues often have the effect of altering pagination, which compromises the accuracy of $\mathsf{Pr} \infty \mathsf{fWiki}$.

Instead, **always** use the chapter, section and entry, depending on how the work is organised. Please add chapter and section titles if they are available.

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

== Sources == * {{BookReference|Naive Set Theory|1960|Paul R. Halmos|prev = Union of Singleton|next = Union with Empty Set}}: $\S 4$: Unions and Intersections * {{BookReference|Topology|1961|John G. Hocking|author2 = Gail S. Young|prev = Definition:Set Equality/Definition 2|next = Definition:Set Intersection}}: A Note on Set-Theoretic Concepts * {{BookReference|Abstract Algebra|1964|W.E. Deskins|prev = Equivalence of Definitions of Set Equality|next = Definition:Set Intersection}}: $\S 1.1$: Definition $1.2$ * {{BookReference|Point Set Topology|1964|Steven A. Gaal|prev = Definition:Set Union/Set of Sets|next = Union is Commutative}}: Introduction to Set Theory: $1$. Elementary Operations on Sets * {{BookReference|Limits and Continuity|1964|William K. Smith|prev = Definition:Binary Operation|next = Definition:Set Intersection}}: $\S 2.1$: Sets * {{BookReference|Probability Theory|1965|A.M. Arthurs|prev = Definition:Subset/Euler Diagram|next = Definition:Set Union/Venn Diagram}}: Chapter $1$: Set Theory: $1.3$: Set operations * {{BookReference|Programming, Games and Transportation Networks|1965|Claude Berge|author2 = A. Ghouila-Houri|prev = Definition:Indexed Family of Sets|next = Definition:Union of Family}}: $1$. Preliminary ideas; sets, vector spaces: $1.1$. Sets * {{BookReference|Sets and Groups|1965|J.A. Green|prev = Empty Set is Subset of All Sets/Proof 1|next = Intersection is Subset of Union}}: $\S 1.4$. Union * {{BookReference|Modern Algebra|1965|Seth Warner|prev = Associative and Anticommutative|next = Definition:Set Intersection}}: Chapter $\text I$: Algebraic Structures: $\S 3$: Unions and Intersections of Sets

## Types of sources

There are several templates that can be used:

### Hardcopy Sources

- Template:BookReference
- This 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:

- 1969: C.R.J. Clapham:
*Introduction to Abstract Algebra*: $\S 4.17$: Theorem $28$

which can be found on the page Characteristic times Ring Element is Ring Zero.

- Template:Citation
- This 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:

- 1908:
*Mathematical Logic as Based on the Theory of Types*(*Amer. J. Math.***Vol. 30**: pp. 222 – 262)

which appears on the page for Bertrand Russell.

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.

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

Example:

- Weisstein, Eric W. "Circular Sector." From
*MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/CircularSector.html

which can be found in the page Area of Sector.

- Template:Planetmath
- This provides a direct link to a page on the https://planetmath.org/ website.

Example:

*This article incorporates material from Urysohn's Lemma on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.*

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

- Template:MacTutor Biography
- This provides a direct link to a page on the https://mathshistory.st-andrews.ac.uk/ website.

Example:

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

- Template:KhanAcademy
- This provides a direct link to the Khan Academy.

Example:

- For a video presentation of the contents of this page, visit the Khan Academy.

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

- Template:Metamath
- This provides a direct link to Metamath.

Example:

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

- Template:Mizar
- This provides a direct link to Mizar.

Example:

- Mizar article TOPGEN_1:10

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

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

Example:

- This sequence is A002193 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008).

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

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

Example:

- Ring. O.A. Ivanova (originator),
*Encyclopedia of Mathematics*. URL: https://www.encyclopediaofmath.org/index.php?title=Ring

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

- Template:Stackexchange
- This provides a direct link to a page on Mathematics Stack Exchange.

Example:

- robjohn (https://math.stackexchange.com/users/13854/robjohn), How to prove that $\ds \lim \limits_{x \mathop \to 0} \frac {\sin x} x = 1$?, URL (version: 2013-06-19): https://math.stackexchange.com/q/75151

which can be found in the page Derivative of Sine Function/Proof 5.

It is **highly recommended** that the above resource is **not** used except in the following circumstances:

- $(1): \quad$ OP has sweated bullets of blood trying to solve a problem or prove a theorem. When all else has failed, they ask at StackExchange, and someone comes up with an answer.

- $(2): \quad$ After searching high and low in the literature and online, the only place where a certain result or definition can be found documented is on StackExchange.

Also, please note that the only acceptable link is to an **answer**, not a **question**. Make sure you understand exactly what you are linking to.

Other invocations of material from that resource is likely to be peremptorily deleted.

### 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, because for example:

- a theorem contains multiple statements
- a proof contains in fact multiple proofs
- 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.