Positive eigenvalues and two-letter generalized words. Hillar, C.; Johnson, C.R.; Spitkovsky, I.M. — 2002 ELA. The Electronic Journal of Linear Algebra [electronic only]
Positive Matrix Functions on the Bitorus with Prescribed Fourier Coefficients in a Band. M. Bakonyi; L. Rodman; I.M. Spitkovsky; H.J. Woerdeman — 1999 The journal of Fourier analysis and applications [[Elektronische Ressource]]