Bethe-Salpeter wave functions of ηc(1S, 2S) and ψ(1S, 2S) states: local-potential description of the charmonium system revisitedKazuki Nochi, Taichi Kawanai and Shoichi SasakiEPJ Web Conf., 175 (2018) 06009DOI: https://doi.org/10.1051/epjconf/201817506009