# There were undefined references

This error appears when ** \ref{...}** is used and LaTeX is unable to find the corresponding label. There are three ways in which this can happen.

- There is a typo in
`\label{...}`

- There is a typo in
`\ref{...}`

- A label has been forgotten.

An example is shown below

```
\section{introduction}\label{introduction}
A typo when referencing the introduction would be \ref{intorduction}.
Another error is referencing a label which has never been defined such as \ref{section1}
```

Each of these will generate an error which looks like

main.tex, line 6

main.tex, line 6

main.tex, line 6

To avoid this, we must always make sure that when we use ** \ref{...}**, that there is a corresponding

**, and that the arguments of**

`\label{...}`

**and**

`\ref{...}`

**are the same.**

`\label{...}`

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