We defined gray literature as any non-peer-reviewed literature that met the studys inclusion criteria. This included presentations, articles, white papers, trade publications, issue briefs, and books. We did not include articles from magazines or newspapers.
To scan the gray literature, we examined the HHS web-site and the web-sites suggested by the project team. We also conducted a more targeted web search based on some of the findings from the peer-reviewed literature (see Appendix A for the list of web-sites we reviewed).