# TexLive References

**Cross-references** link to sections, figures, tables, and equations using `\label` and `\ref`. Place `\label{key}` after a section heading, caption, or equation, then use `\ref{key}` or `\eqref{key}` (for equations) to insert its number.

```latex
\section{Introduction}
\label{sec:intro}

In Section \ref{sec:intro}, we...

\begin{equation}
E = mc^2
\label{eq:einstein}
\end{equation}

From equation \eqref{eq:einstein}, we derived...
```

Compile twice for references to resolve: first pass creates `.aux` file with labels, second pass reads it and inserts numbers. Always use `~` (tilde) to prevent line breaks: `Section~\ref{sec:intro}` not `Section \ref{sec:intro}`.

**Citations** reference sources in a bibliography. LaTeX uses BibTeX: create a `.bib` file with bibliography entries, then cite them with `\cite{key}`:

```latex
\documentclass{article}
\usepackage{natbib}
\begin{document}

As shown in \cite{einstein1905}, relativity...

\bibliographystyle{plain}
\bibliography{references}
\end{document}
```

The `.bib` file (`references.bib`) contains entries:

```bibtex
@article{einstein1905,
  author = {Einstein, Albert},
  title = {On the Electrodynamics of Moving Bodies},
  journal = {Annalen der Physik},
  year = {1905}
}

@book{knuth1984,
  author = {Knuth, Donald E.},
  title = {The TeXbook},
  publisher = {Addison-Wesley},
  year = {1984}
}
```

`\bibliographystyle{plain}` sets citation format (plain, apalike, natbib, etc.). `\bibliography{references}` includes the `.bib` file (omit `.bib` extension).

To generate the bibliography, compile with: `pdflatex main.tex && bibtex main && pdflatex main.tex && pdflatex main.tex`. The `bibtex` command generates the formatted bibliography from the `.bib` file. Two final `pdflatex` runs resolve references.

**Citation styles:** `\cite{key}` produces a number `[1]` or author-year depending on the bibliographystyle. `\citet{key}` (textual) produces "Author (Year)"; `\citep{key}` (parenthetical) produces "(Author Year)". Requires `natbib` package.

**URL citations:** Use `@misc` entries for websites:

```bibtex
@misc{wikipedia2024,
  author = {Wikipedia},
  title = {Article Title},
  url = {https://...},
  year = {2024}
}
```

**Hyperref integration:** With `\usepackage{hyperref}`, citations become clickable links to the bibliography.