1. A. Erdélyi (ed.), Higher Transcendental Functions. Vol. III (Bateman Manuscript Project, California Inst. Tech., 1981).
2. V. L. Vaskevich, “Embedding constants for periodic Sobolev spaces of fractional order,” Sib. Mat. Zh. 49, 1019 (2008) [SiberianMath. J. 49, 806 (2008)].
3. V. L. Vaskevich, “The error and guaranteed accuracy of cubature formulas in multidimensional periodic Sobolev spaces,” Sib. Mat. Zh. 55, 971 (2014) [SiberianMath. J. 55, 792 (2014)].
4. S. L. Sobolev, “Convergence of cubature formulas on infinitely differentiable functions,” Dokl. Akad. Nauk SSSR 223, 793 (1975) [Sov.Math., Dokl. 16, 991 (1975)].
5. E.W.Weisstein, Sum of Squares Function (MathWorld–AWolframWeb Resource, http://mathworld.wolfram.com/SumofSquaresFunction.html).