permitted_uri_chars

[eluser]yorvik[/eluser]
Hello guys

I want to allow these carachters in my URL: Ö , Ü , ï.
I know I have to edit this line:

Code:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-';

But I don't know what the regular expression should be.

Thanks in advance

Joachim