### 4.3. How to cite a reference

To cite a reference in your paper, you need to know the reference key from the BibTeX entry (see Section 4.2, “An example BibTeX file”).

There are two ways to cite a reference:

#### 4.3.1. Numbered reference citations

If the preferred style in your discipline is to cite references using numbers in square brackets like [17], follow these steps.

1. In your `.tex` file, modify the line that imports the `natbib` package so it looks like this.

```\usepackage[square,numbers]{natbib}
```
2. At the point in your text where you want to cite the reference, use this LaTeX command:

```\cite{`KEY`}
```

The `KEY` is the reference key for that citation, as defined in the reference's entry in your `.bib` file.

For example, suppose the work has the key `knuth1983`, and it happens to be the 19th reference in your bibliography. Then this LaTeX sentence:

```    The TeX system was first described in \cite{knuth1983}.
```

will appear in your paper as “The TeX system was first described in [19].”

#### 4.3.2. Author-year reference citations

The preferred style in some disciplines is to cite references using the author's name and year of publications. Here are some examples in context.

• See (Knuth, 1983).

• See Knuth [1983].

• Knuth's 1983 work states….

By default, the `nmtsrsab2012.sty` style file will use parentheses. If you prefer square brackets, edit the line that imports the `natbib` package to look like this:

```\usepackage[square]{natbib}
```

If you prefer the author-year citation format, there are several different ways to cite the work. Here are some of the most common forms, and how they will appear in your paper. Suppose the work has the key `knuth1983`, the author's name is Knuth, and the year of publication is 1983.

 `\citet{knuth1983}` Knuth, (1983) `\citep{knuth1983}` (Knuth, 1983) `\citeauthor{knuth1983}` Knuth `\citeyear{knuth1983}` 1983