Volume 15, Issue 3 Janusz Matkowski Quadratic inequalities and a characterization of inner product Downloads Abstract PDF Full article PDF DOI { copied = true; setTimeout(() => copied = false, 2000) })" :aria-label="copied ? 'DOI copied' : 'Copy DOI'" :title="copied ? 'Copied' : 'Copy DOI'" > Find all available articles from these authors Janusz Matkowski Find more articles with the same keywords parallelogram equality inner product quadratic functional quadratic inequality Jordan-von Neumann theorem Find more articles with the same subject classes 46C15 26D15 39B22 39B55