Whyburn has proved that each open mapping defined on arc (a simple closed curve) is light. Charatonik and Omiljanowski have proved that each open mapping defined on a local dendrite is light. Theorem 3.8 is an extension of these results.
@article{118719, author = {W\l adys\l aw Makuchowski}, title = {On open light mappings}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {35}, year = {1994}, pages = {779-788}, zbl = {0830.54014}, mrnumber = {1321248}, language = {en}, url = {http://dml.mathdoc.fr/item/118719} }
Makuchowski, Władysław. On open light mappings. Commentationes Mathematicae Universitatis Carolinae, Tome 35 (1994) pp. 779-788. http://gdmltest.u-ga.fr/item/118719/
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