3.1 Characterization of the literature
A total of 165 studies were identified by the search strategy after removing duplicates. The title and abstract screening excluded 85 studies. The full text was obtained for 76 peer-reviewed papers, 13 conference proceeding from SIL, which included AASV (n = 6), IPVS (n = 6) and Leman (n = 1), one from AAVLD, one from ACVP conference proceedings. No proceedings were extracted from CRWAD. Three studies (Ding et al., 1983; Geyer et al., 1994; Lan et al., 2012) were excluded because did not have an available full text. From 76 studies, 48 were excluded in the second stage after full-text screening including 42 nonrelevant papers, four review papers, and one non-English paper. Finally, 29 studies were identified as relevant to the review (Fig 1).