From the introduction: Following A. A. Gonchar et al. [in: Progress in approximation theory. An international perspective. Proceedings of the international conference on approximation theory, Tampa, South Florida, USA, March 19–22, 1990. New York: Springer-Verlag. 169–190 (1992; Zbl 0795.41013)], wie study the diagonal Frobenius-Padé approximants \(\Phi_n:= \Phi_{n-1,n}=P_{n-1}/Q_n\) for markov functions \(f\), that is, Cauchy transforms of psotive Borel measures \(\sigma\) with \(\operatorname{supp} \sigma\subset[c;d]\subset\mathbb{R}\), \(b<c\):
\[ f(z):=\widehat{\sigma}(z)=\int_c^d\frac{d\sigma(t)}{t-z}. \]