@article{Bondarenko_Stepochkina_2009, title={Description of posets critical with respect to the nonnegativity of the quadratic Tits form}, volume={61}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/3045}, abstractNote={We present the complete description of finite posets whose Tits form is not nonnegative but all proper subsets of which have nonnegative Tits forms. A similar result for positive forms was obtained by the authors earlier.}, number={5}, journal={Ukrains’kyi Matematychnyi Zhurnal}, author={Bondarenko, V. M. and Stepochkina, M. V.}, year={2009}, month={May}, pages={611-624} }