However, because I'm writing a methods-focused review -- we only look at RCTs meeting certain (pretty minimal) criteria relating to statistical power and measurement validity -- what I'm doing is closer to a combination of review of previous reviews (there have been dozens in my field) and a snowball search (searching bibliographies of papers that are relevant). I also consulted with experts in the field. however, finding bachelor's theses has been challenging, but many are actually relevant, so undermind was helpful there.