Iam working on a thesis about Tove Jansson as a Swedish.finnish author. Do You know a library or archiv speziallised on her?

There is no special library dedicated to Tove Jansson, but in Tampere You can study Tove Jansson's Moomin works in a special museum called The Tampere Art Museum - Moomin Valley. The Museum is situated in the Tampere main library and it has a collection of Tove Jansson drawings and miniature works. More info on page
http://www.tampere.fi/muumi/english/index.htm.
The Exhibition even has a small database (in finnish) of the contents of Moomin books.
The Finnish Institute for Children's Literature -
Documentation and Information Centre for Finnish Children's Literature collects the works of finnish children's authors and also the studies and reference works. This Institute is also here in Tampere (http://www.tampere.fi/kirjasto/sni/sneinfo.htm).

The Finnish National Libraty in Helsinki
http://www.lib.helsinki.fi/english/index.htm
acquires and preserves all finnish publications as well as maintains its collections of research material and for provides access to them. The Finnish National Bibliography contains information of all publications printed in Finland or publications published outside Finland but with a Finnish author or related to Finland. You can search this database in english, too http://fennica.linneanet.fi/cgi-bin/Pwebrecon.cgi?LANGUAGE=English&DB=l….

Here are some links to pages about Tove Jansson in Internet :

http://www.wsoy.fi/index.jsp?c=authors&auth_cat=1&id=51&lastname=Jansso…

http://www.kirjasto.sci.fi/tjansson.htm

http://virtual.finland.fi/finfo/english/jansson.html

http://www.lysator.liu.se/nordic/authors/tove_uk.html

http://www.hut.fi/~svilja/muumi_links.html

http://www.muumimaailma.fi/ (Moomin World themepark in Naantali)