The original work of this tool is:
Rodrigo Agerri, Josu Bermudez and German Rigau (2014): "IXA pipeline: Efficient and Ready to Use Multilingual NLP tools", in: Proceedings of the 9th Language Resources and Evaluation Conference (LREC2014), 26-31 May, 2014, Reykjavik, Iceland.
IXA pipes is a modular set of Natural Language Processing tools (or pipes) which provide easy access to NLP technology for several languages. It offers robust and efficient linguistic annotation to both researchers and non-NLP experts with the aim of lowering the barriers of using NLP technology either for research purposes or for small industrial developers and SMEs. Here you can find an implementation of their Statistical Part of Speach (POS) tagging for Portuguese.