@misc{Pérez_García_Víctor_Fixed,
 author={Pérez García, Víctor and Fetter Nathansky, Helga},
 howpublished={online},
 publisher={nakł. UMCS},
 language={eng},
 type={artykuł},
 title={Fixed points of periodic mappings in Hilbert spaces},
 keywords={matematyka},
}