Institut Mittag-Leffler publishes two well-renowned mathematical journals: 

Acta Mathematica 
Arkiv för matematik

There is also a Preprint Series published in connection with the scientific programs held at the institute.

For those interested in the life of the Institute´s founder Gösta Mittag-Leffler, a well written biography was published in 2007 (with an english translation published 2010).