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2. “Leçons d'Analyse Fonctionelle.”;Riesz,1952
3. On a topological problem connected with the Cantor-Bernstein theorem;Kuratowski;Fund. Math.,1950
4. Open and closed mappings;Whyburn;Duke Math. J.,1950
5. On the distinction of right and left at points of discontinuity;Young;Quart. J. Math.,1908