**Extramples**

Here I show some examples with a discussion of peculiar issues. Some other also interesting remarks can be found in the bout page of TTao’s blog *What’s *.

### Example 1

** \langle q | f ( \hat{q} ) = f (q) \langle q |**

Notice that the \left and \right are not necessary in this case, however, if used it will work:

** \left \langle q | f ( \hat{q} ) = f (q) \langle q |**