Star formation in outer rings of S0 galaxies - I. NGC 6534 and MCG 11-22-015 O. Sil’chenko, I. Kostiuk, A. Burenkov and H. Parul A&A, 620 (2018) L7 Published online: 05 December 2018 DOI: 10.1051/0004-6361/201834392