Custom keywords not linking for particular pattern

I have found a pattern for which custom keywords is not working.
There is problem with special letters ä, ö, å
Custom Keywords :
1. meäts, http://www.google.com
2. tillhört, http://www.rediff.com
3. Elektrobitissä, http://www.git.com
4. tillhrtö, http://www.rediff.com

So out of the above keywords, 1 and 2 works.
3 and 4 does not work.
If word ends with those special letters, word is not links otherwise if letter appears in any position except last, it works.

How can I solve this problem, plz help!
http://wordpress.org/extend/plugins/seo-automatic-links