How to cite Wolfram Web Resources in Bibtex?

Question

Wolfram offers very helpful web resources for mathematical terminology.

Every article has a short note at the end, e.g. in Tree it says:

CITE THIS AS:

Weisstein, Eric W. "Tree." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Tree.html

What is the correct way to produce a BibTex entry with this information? Where to put "From MathWorld--A Wolfram Web Resource"? How to clarify that the date refers to the date of retrieval?

I suggest something like:

@electronic{weisensteinTree,
    author = {Weisstein, E. W.},
    title = {Tree}
    ...
    ?
}

Answer 1

You mention that you use BibTeX and the plainnat bibliography style. Unfortunately, this bibliography style does not recognize an @electronic entry type. However, the @misc entry type is sufficiently general to meet your needs. Try the following form of the entry, which assumes that you're also loading the url LaTeX package:

@misc{weisstein,
    author   = {Weisstein, Eric W.},
    title    = {Tree. {From MathWorld---A Wolfram Web Resource}},
    url      = {\url{http://mathworld.wolfram.com/Tree.html}},
    note     = {Last visited on 13/4/2012},
}

The curly braces around "From ... Resource" are there to keep BibTeX/plainnat from converting any uppercase letters inside the group into lowercase. Encasing the URL in an explicit \url{...} macro serves to let LaTeX find, if needed, convenient line break points. (By default, long URL strings will not be broken up across lines, potentially leading to seriously overfull or underfull lines.)

(Shameless self-promotion alert!) For more information on this subject, see also the answers to the questions Customizing Bibliography alpha and urldate in BibTeX gets ignored.

Answer 2

Checking the biblatex documentation, I found the online reference that seems to serve your purpose:

@online{weissteinTree,
    author   = {Weisstein, Eric W.},
    title    = {Tree},
    subtitle = {From MathWorld--A Wolfram Web Resource},
    note     = {Visited on 13/04/12},
    url      = {http://mathworld.wolfram.com/Tree.html}
}

The result is:

E.W. Weisstein. Tree. From MathWorld–A Wolfram Web Resource. Visited on 13/04/12. URL: http://mathworld.wolfram.com/Tree.html