# Re: How to install new packages to Lyx?

```On 08/31/2009 06:22 PM, ilias andronos wrote:
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```sorry for insisting but i tried searching with google how to enter these
characters and i came accross hep package again..i don't
understand..what is ERT?what exactly do i have to type in math mode in
order to get the slashed characters??```
```
```
Let's say a slashed "a" is entered in LaTeX as: \slasheda. (I have no idea what it really is. Presumably the hep manual will tell you.) Then in math mode, enter "\slasheda" and then a space. You'll see exactly that, but if you View>DVI ir View>PDF or whatever (and have \usepackage{hep} in your preamble), then you'll see the slashed character in the output. It's just that LyX doesn't know how to display it, so it displays the raw LaTeX.
```
```
As for ERT, this is also called "TeX Mode", and it's activated by Insert>TeX Mode. It again allows you to insert raw LaTeX into the document.
```
rh

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