On the numerical index with respect to an operatorVladimir Kadets, Miguel Martín, Javier Merí, Antonio Pérez, Alicia Quero
Dissertationes Mathematicae 547 (2020), 1-58 MSC: Primary 46B04; Secondary 46B20, 46B25, 46L05, 47A12, 47A30.DOI: 10.4064/dm805-9-2019