The nature of the methanol maser ring G23.657–00.127 - II. Expansion of the maser structure A. Bartkiewicz, A. Sanna, M. Szymczak, L. Moscadelli, H. J. van Langevelde and P. Wolak A&A, 637 (2020) A15 Published online: 05 May 2020 DOI: 10.1051/0004-6361/202037562