John R. Akeroyd, Kristi Karber, Alexander Yu. Solynin, “Minimal Kernels, Quadrature Identities and Proportional Harmonic Measures”, Rocky Mountain J. Math., 36:6 (2006)
Boris Shapiro, Alek Vainshtein, “On the number of connected components in the space of M-polynomials in hyperbolic functions”, Advances in Applied Mathematics, 30:1-2 (2003), 273