When the amount of resulting hits is too high to be managed within the available timeframe / resources, search limits may be applied.
First, tools related to the Thesaurus should be considered:
Several search interfaces provide search limits that can also be applied to narrow the search. Classical examples are date and language limits, but some databases also provide limits according to age, gender, publication type etc. Before applying search limits, the risk of a too specific (i.e. narrow) search should be considered.