1. S. Akiyama, S. Egami and Y. Tanigawa, Analytic continuation of multiple zeta-functions and their values at non-positive integers, Acta Arith. 98, no. 2 (2001), 107–116.
2. S. Akiyama and H. Ishikawa, On analytic continuation of multiple L-functions and related zeta-functions, ‘Analytic Number Theory’, edited by C. Jia and K. Matsumoto, Kluwer (2002), 1–16.
3. T. Arakawa and M. Kaneko, Introduction to multiple zeta values (in Japanese), MI Lecture Note Series 23 (2010), 1–111.
4. K-W. Chen, C-L. Chung and M. Eie, Sum formulas of multiple zeta values with arguments multiples of a common positive integer. J. Number Theory 177 (2017), 479–496.
5. L. Euler, Meditationes circa singulare serierum genus, Novi Comm. Acad. Sci. Petropol 20 (1775) 140-186, Reprinted in: Opera Omnia Ser. I, vol. 15, Teubner, Berlin, 1927, pp. 217–267.