Although presented here as a step by step process, the overall sequence of a literature search is not linear. It is more of a circular path in which you find some material, read it, then using the information you found, refine your search terms and go back and search again. That circle may need to be repeated more than once for each database and don't forget that the process must be used in every resource that you try.
The process will take time and you'll find that you can't do it all at once. You don't want to waste time repeating work you've already done, so as you go thru the process, keep track of what databases you've searched and what search strategies you've used in each database.
Three different methods are outlined below: Subject, Author and Citation. Although there will be overlap in the results you get, each method will find unique items that the other two searches couldn't.
- Subject Search
Subject searching involves looking for not only how you describe the concepts of the topic but also how the authors and the databases describe the concepts.
- Start with a search that uses your terminology for the concept(s)
Expand the search to include synonyms for the concept(s)
- If you created a PICO statement, enter the keyword(s) you used to describe your concepts of P AND I
- If you retrieve too many items, narrow the search by restricting the words to the title field (not every database allows this)
- Examine the titles and abstracts (summaries) in the results list - you're looking for other terminology the authors may use to describe the P and I concepts
- Also examine the results list for the controlled vocabulary (subjects) that the database assigned to them
Search using the database's controlled vocabulary for the concept(s)
- Redo your search, this time using the synonyms or different terminology that you know about and also the author terminology you discovered from reading the results of your original search
- Again, examine your results list looking not only for applicable articles but also synonyms or different terminology you haven't already found - if you find other synonyms/terminology, go back and redo the search with these new terms
Review the items you retrieved from your keyword/controlled vocabulary searches.
- In some databases, the controlled vocabulary may be called the Subjects, Indexing Terms, Thesaurus, or Descriptors.
- Some databases, such as Google Scholar, Library One Search and Web of Science, do not use controlled vocabulary, so you wouldn't be able to use this strategy in them. However you can use controlled vocabulary terminology from the other databases in your keyword/synonym searches in the uncontrolled databases.
- Use the abstract, introductory section, and conclusion to determine if you need to fully read (and keep) this item
- Also keep in mind your C (comparison) and O (outcome) concepts - these will also help you decide if the item is worthwhile to pursue in more detail.
- Keep looking for the different terminology that authors and databases might use. If you find new terminology, go back and search the databases again using those words.
Is there an author or organization that repeatedly shows up in your list of "keeper" articles? Find out what other items that author or organization produced. Did you find new terminology for your concepts? If yes, go back and search the databases again using those words. Are you finding other prominent authors? Search those as well.
For the most important items you found, use citation searching to find even more related items:
- Go backwards in time by finding the references cited in the document (may be called the bibliography)
You'll discover what this author thought was important.
- Go forwards in time by finding the articles (using Web of Science and Google Scholar) that cite this document
You'll discover how this item affected future research, including in areas not covered by your subject search.
- Did you find new terminology for your concepts? If yes, go back and search the databases again using those words. Are you finding new prominent authors? Search those as well.