@misc{Lech_Jacek_On,
 author={Lech, Jacek and Rybicki, Tomasz},
 howpublished={online},
 publisher={nakł. UMCS},
 language={eng},
 title={On the perfectness of groups of diffeomorphisms with no restriction on support},
 type={artykuł},
 keywords={matematyka},
}