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3. 3. V. M. Bondarenko, M. V. Stepochkina, "(Min, max)-equivalency of posets and non-negative Tits forms," Ukr. Mat. Zh., 60, No. 9, 1157-1167 (2008)
4. English translation: Ukr. Math. J., 60, No. 9, 1349-1359 (2008), https://doi.org/10.1007/s11253-009-0147-7
5. 4. V. M. Bondarenko, M. V. Stepochkina, "Description of posets critical with respect to the nonnegativity of the quadratic Tits form," Ukr. Mat. Zh., 61, No. 5, 611-624 (2009)