Brazilian portuguese keyboard and accented characters (á, ç, ã)

[Markos]

Hi

I just installed Jessie in an IBM ThinkPad X60.
When I select the Keyboard "en" the keys work properly but can not 
generate non-English characters or accented characters, such as ç, ã  or á.

At another laptop (ThinkPad Z61) I type:

' + c -> ç
' + a -> á
~ + a -> ã
...

How to configure the IBM ThinkPad X60 keyboard to do the same?

Thanks,
Markos