Markosyan, S. E., and A. H. Khachaturyan. 2009. “OPTIMAL LEVEL PLACEMENT OF THE TRANSITIVE ORIENTED AND BIPARTITE ORIENTED GRAPHS BY HEIGHT”. Proceedings of the YSU A: Physical and Mathematical Sciences 43 (2 (219). Yerevan, Armenia:43-49. https://doi.org/10.46991/PYSU:A/2009.43.2.043.