I must be doing something wrong.

I define the following integral:

The code:

```
! (
* SubsuperscriptBox[([Integral]), ( (- W ) / 2 ), (W / 2 )] (
* SubsuperscriptBox[([Integral]), ( (- L ) / 2 ), (L / 2 )]a[
x] [DifferentialD]X [DifferentialD]Y ) )
```

… and I get it:`W a[x]`

as a result ??

Should be:

From a[x] It is an undefined function of x.

EDIT: If I enter it using the "Entry Form" and not the "traditional form":

```
To integrate[Tointegrate[a[Integrate[to[Integrar[una[Integrate[a[x], {x, -L / 2, L / 2}], {y, -H / 2, H / 2}]
```

Mathematica understands it, and I get the correct result.

**Why is that ?**

EDIT 2: putting it in parentheses does not help:

EDIT 3: Put the parathon around the internal integral, solve the problem, but I do not understand why I have to do that Mathematica should automatically see where the integral starts and ends.