The model of vehicle optimum quantity for grain crop harvesting under the conditions of farming in Poltava regionVolodymyr Zagoryanskii, Olena Zagoryanskya, Tetyana Haykova and Volodymyr KhorolskiiSHS Web Conf., 67 (2019) 03013DOI: https://doi.org/10.1051/shsconf/20196703013