Hi,

I was learning how to use the Fierz identity using the manual and a notebook in tutorials.

(Eventually, I understood why I got stuck with it: I was sloppy on mentioning the range of the indices explicitly. Sorry, Kasper.)

Anyway,

I found a typo in the tutorial of Fierz transformations:

```
fierz(_, $\theta, \epsilon, \psi_{\mu}, \psi_{\nu}$ );
```

should be replaced with

```
fierz(_, $\theta, \epsilon, \psi_{\mu}, \psi_{\rho}$ );
```

This is what I got stuck with for a while :) Thanks.