O některých Banachových problémech
On measure for projectors
An example of a finite set of projectors in is exhibited for which no 0-1 measure exists.
On measure for projectors. II
On a characterisation of inner product spaces.
On a Class of Normaloid Operators.
On a completion of prehilbertian spaces.
On a functional representation of the lattice of projections on a Hilbert space
On a Functional Which is Quadratic on A-orthogonal Vectors
On a functional-analysis approach to orthogonal sequences problems.
Sea T un operador lineal acotado e inyectivo de un espacio de Banach X en un espacio de Hilbert H con rango denso y sea {xn} ⊂ X una sucesión tal que {Txn} es ortogonal. Se estudian propiedades de {Txn} dependientes de propiedades de {xn}. También se estudia la ""situación opuesta"", es decir, la acción de un operador T : H → X sobre sucesiones ortogonales.
On a generalized -inner product and the corresponding Cauchy-Schwarz inequality.
On a lattice characterization of Hilbert spaces
On a new method in intuitionist linear analysis
On a Problem of H. Berens.
On a property of Gram's determinant.
On a superadditivity property of Gram's determinant.
On (a,b,c,d)-orthogonality in normed linear spaces
We first introduce a notion of (a,b,c,d)-orthogonality in a normed linear space, which is a natural generalization of the classical isosceles and Pythagorean orthogonalities, and well known α- and (α,β)-orthogonalities. Then we characterize inner product spaces in several ways, among others, in terms of one orthogonality implying another orthogonality.
On adjoint of an operator on reflexive Banach spaces
On an -Birkhoff orthogonality.
On certain trigonometric sums in several variables.
On characterizations of inner-product spaces.