@misc{Cellina_Arrigo_Some,
 author={Cellina, Arrigo},
 howpublished={online},
 publisher={Wydawnictwo Uniwersytetu Śląskiego},
 publisher={De Gruyter Open},
 language={eng},
 title={Some problems in the Calculus of Variations},
 type={artykuł},
 keywords={matematyka},
}