Grammar errors and confusing discriptions

On page 329, 
```
The advantage of using the functional index is that is it more explicit what you want
to index, and you do not have the extra BirthMonth column. 
```

I think it should be 

```
The advantage of using the functional index is that it is more explicit about what you want
to index, and you do not have the extra BirthMonth column. 
```