. 2015 Oct 7;10(10):e0139216. doi: 10.1371/journal.pone.0139216
© 2015 Matsui et al
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
Fig 1. Hospital volume and risk-standardized mortality ratio.
