Search and selection process.. Two search phases will provide evidence to contribute jointly to both the narrative synthesis and literature review. The screening stage of selection (nearly complete) applies a checklist (Figure 2); the first five items and one of the last two items must be met to include the literature, which will be classified later as being empirical or non-empirical. Ambiguous items will be read in full and discussed by two or possibly three reviewers. Further selection or rejection will be completed after reading full reports and categorizing them as contributing to the narrative synthesis or literature review. Grey literature is being rejected at the screening stage if it is not considered to be of sufficient relative importance (Table 1, categories 1, 2 & 3) as determined by AcademyHealth . Grey-literature reports describing empirical research will be placed in the narrative synthesis if deemed to have sufficient quality (category A, in accordance with McGrath et al..