One option is to present your search strategy in a table:
Don't forget to add which databases you have used in your search, and which date.
Additional searches that may be difficult to report in a table you can describe in the text. Here are a few examples:
- Chain searching was used as the reference lists in the articles gave more relevant references...
- A search within the EU webpage gave several relevant reports...
- A complementary search in Google on search words X, Y and Z gave an additional few relevant references...
