Developing a Stemmer for German Based on a Comparative Analysis of Publicly Available Stemmers
Leonie Weißweiler, Alexander Fraser
GSCL 2017

Stemmers, which reduce words to their stems, are important components
of many natural language processing systems. In this paper, we conduct
a systematic evaluation of several stemmers for German using two gold
standards we have created and will release to the community. We then
present our own stemmer, which achieves state-of-the-art results, is
easy to understand and extend, and will be made publicly available
both for use by programmers and as a benchmark for further stemmer
development.

The stemmer is available at: 

https://www.github.com/LeonieWeissweiler/CISTEM