@article{AULFM_1989_03_a3,
     author = {Rzepecka, Genowefa},
     title = {On {Density} of {Pairs} of {Natural} {Numbers}},
     journal = {Acta Universitatis Lodziensis. Folia Mathematica},
     year = {1989},
     volume = {03},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AULFM_1989_03_a3/}
}