1. A. S. Belov, “On positive definite piecewise linear functions and their applications,” in Trudy Mat. Inst. Steklova, Vol. 280: Orthogonal Series, Approximation Theory, and Related Problems (MAIK Nauka/Interperiodica, Moscow, 2013), pp. 11–40 [Proc. Steklov Inst. Math. 280 (5-33) (2013)].
2. W. Feller, An Introduction to Probability Theory and Its Applications (John Wiley & Sons, New York, 1966), Vol. II.
3. Z. Sasvári, Positive Definite and Definitizable Functions (Akademie Verlag, Berlin, 1994).
4. T. M. Bisgaard and Z. Sasvari, Characteristic Functions and Moment Sequences. Positive Definiteness in Probability (Nova Sci. Publ., Huntington, NY, 2000).
5. R. R. Goldberg, “Restrictions of Fourier transforms and extension Fourier sequences,” J. Approximation Theory 3(2), 149–155 (1970).