The concepts in this guide can be applied to any type of information searching. Usually literature searching involves electronic abstract/index/full-text services, but the same procedures work with Web searching, printed index services, and even non-published information.
"The right answer is always 50 references."
Searches should be constructed so that the results set is small enough to obtain and review the results in a reasonable time frame, but large enough to consider a different approach if the field is too narrow. If there are 200 "good" articles, then limit by date, language, type, etc. If there are only 20 "good" articles, then look for others on closely-related concepts. If you used the Venn diagram approach, add more groups or more synonyms in each group. Hint: use the subject terms that describe the articles you like best in the results you've found so far. If you used the filter approach, add or remove filters until you reach an acceptable level of results.