@misc{Gorawski_Marcin_Grouping,
 author={Gorawski, Marcin and Marks, Paweł},
 howpublished={online},
 publisher={Wydaw. Uniwersytetu Marii Curie-Skłodowskiej},
 language={eng},
 type={artykuł},
 title={Grouping and joining transformations in the data extraction process},
}