O'Sullivan E. et al.The dark haloes of early-type galaxies in low-density environments: XMM-Newton and Chandra observations of NGC 57, 7796 and IC 1531// Monthly Notices of the RAS.— 2007.— Vol.380.— P.1409-1421.— doi:10.1111/j.1365-2966.2007.12229.x.— Bibcode:2007MNRAS.380.1409O,{{bibcode}}: Проверьте bibcode: length (справка).
O'Sullivan E. et al.The dark haloes of early-type galaxies in low-density environments: XMM-Newton and Chandra observations of NGC 57, 7796 and IC 1531// Monthly Notices of the RAS.— 2007.— Vol.380.— P.1409-1421.— doi:10.1111/j.1365-2966.2007.12229.x.— Bibcode:2007MNRAS.380.1409O,{{bibcode}}: Проверьте bibcode: length (справка).