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@article{MAN_1974__208_162568, author = {Paul Georgiou}, title = {A {Semigroup} {Structure} in the {Space} of {Liftings.}}, journal = {Mathematische Annalen}, pages = {195--202}, publisher = {mathdoc}, volume = {208}, year = {1974}, zbl = {0302.46033}, url = {http://geodesic.mathdoc.fr/item/MAN_1974__208_162568/} }
Paul Georgiou. A Semigroup Structure in the Space of Liftings.. Mathematische Annalen, Tome 208 (1974), pp. 195-202. http://geodesic.mathdoc.fr/item/MAN_1974__208_162568/