Rosen Nikolaev, D. Zhelyazkova, T. Milkova. "MINIMIZING THE TRANSPORTATION COSTS BY MEANS OF THREE DIMENSIONAL TRANSPORTATION PROBLEM." 5th International Multidisciplinary Scientific Conference on Social Sciences and Arts SGEM 2018, 2018, pp. 549-556. https://doi.org/10.5593/sgemsocial2018/1.4/S04.071