Citations and cross-references

A document points at its own parts all the time: "by Lemma 2", "see the figure below", "as in the previous section". In LibreTimes Markdown you do that with an ordinary link to an anchor, a name you give the block you want to point at.

Link to a block in the same document

Give the block an anchor with {#name}, then link to #name:

:::theorem[Lagrange]{#lagrange}
The order of a subgroup divides the order of the group.
:::
 
By [Lagrange's theorem](#lagrange), a group of prime order has no proper
subgroups other than the trivial one.

The link takes the reader to the block, and the address of the page with #lagrange at the end is one others can share.

What can carry an anchor:

The rules for a name you choose:

• It starts with a letter, then letters, digits, -, _, . or :, up to 100 characters. Anything else is dropped and the block gets no anchor.
• Use each name once. If two blocks carry the same name, the first one keeps it and links go there.
• A name with a . or a : in it is written {id="eq-2.1"}, because the short # form stops at a dot.
• Pick a name that says what the block is (#lagrange, #fig-orbit), not where it is (#theorem-3): the number changes when you add a theorem above it, and the name does not have to.

The link text is yours to write. Nothing fills in "Theorem 3" for you, so if the statement has a printed number, put it in the link text: [Theorem 3.17](#monotone).

Link to a block in another work

Add the anchor to the other work's address. On the published page, a name you chose has user-content- in front of it, so that it can never clash with the page's own parts; a link inside the same document is adjusted for that automatically, and a link from elsewhere spells it out:

Replace <work-id> with the id in the other work's address.

The [@key] syntax

Square brackets with an @ and a key are reserved for citations resolved against a bibliography and for numbered cross-references:

Today the published page shows this text exactly as you wrote it. It is not yet replaced with an author and year or with "Figure 2". What the syntax does already is keep your text intact:

• [@knuth1974] is never turned into a link to a profile, although a key looks like a mention.
• An address such as ada@example.org is not a citation, because the character before the @ is a letter.
• If any part of a bracket does not parse, the whole bracket is left as ordinary text.

Knuth's analysis [@knuth1974, p. 33] covers the general case.

This is the syntax pandoc reads and writes. A LaTeX or Word file imported on the site does not use it: its citations arrive as numbered markers such as [1], with the bibliography as the work's list of references.

Cite a source today

To give a reader a source they can follow, cite it in a footnote with a DOI or an arXiv link:

The bound is known to be tight.[^knuth]
 
[^knuth]: D. E. Knuth, "Structured programming with go to statements",
    *Computing Surveys* 6 (1974). <https://doi.org/10.1145/356635.356640>