A lemma of Gelfand-Hille type is proved. It is used to give an improved version of a result of Kalton on sums of idempotents.
@article{bwmeta1.element.bwnjournal-article-smv121i2p185bwm, author = {Graham Allan}, title = {Sums of idempotents and a lemma of N. J. Kalton}, journal = {Studia Mathematica}, volume = {119}, year = {1996}, pages = {185-192}, zbl = {0862.46029}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-smv121i2p185bwm} }
Allan, Graham. Sums of idempotents and a lemma of N. J. Kalton. Studia Mathematica, Tome 119 (1996) pp. 185-192. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-smv121i2p185bwm/
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