Study of the dynamics of the coefficient of external friction of seeds crops with shellIgor Khozyaev, Dmitriy Savenkov, Oleg Kirischiev, Ylia Kirischieva and Tatiana TupolskikhE3S Web Conf., 273 (2021) 01032DOI: https://doi.org/10.1051/e3sconf/202127301032