Attribution-NonCommercial-NoDerivs 3.0 United States

This is an open access article, originally published at https://doi.org/10.1186/s12913-018-3686-5
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 3.0 United States This is an open access article, originally published at https://doi.org/10.1186/s12913-018-3686-5