Estimation of pion-emitting source in symmetric and asymmetric collisions using the UrQMD model Eugenia Khyzhniak, Varvara Semenova, Nikita Ermakov and Grigory Nigmatkulov EPJ Web Conf., 204 (2019) 03017 Published online: 03 April 2019 DOI: 10.1051/epjconf/201920403017