@article{10_4064_ap_19_1_47_60,
     author = {M. Kwapisz},
     title = {On the approximate solutions of an abstract equation},
     journal = {Annales Polonici Mathematici},
     pages = {47--60},
     publisher = {mathdoc},
     volume = {19},
     number = {1},
     year = {1967},
     doi = {10.4064/ap-19-1-47-60},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-19-1-47-60/}
}