Engineering: The Literature Review Process

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 searching strategies 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.   The duplicates you retrieve can easily be eliminated by whatever Citation Management software you are using so don't stress about seeing many of the same articles in your results.  It's the unique items being retrieved that will make your search thorough.  

1. 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.
    
   1. Start with a P AND I search  
      • Referring back to your 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 have used to describe the P and I concepts
      • Also examine the results list  for the controlled vocabulary (subjects) that the database assigned to them
        
         
   2. Expand the P AND I search to include synonyms
      • Redo your search, this time including the synonyms/different terminology you know about and the author terminology you discovered in Step 1 above.
      • 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 
        
         
   3. Search using the database's controlled vocabulary for P AND I 
      • In some databases, the controlled vocabulary may be called the Subjects, Indexing Terms, Thesaurus,  or Descriptors.
      • A few databases, such as Google Scholar and Library One Search, do not use controlled vocabulary.  For these databases add those controlled vocabulary terms as part of your synonym searching (Step #2).  
        
         
   4. Review the items you retrieved from your keyword/controlled vocabulary searches.
      • 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 document should be kept and read 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.
         
2. Author Search
   Is there an author or organization that repeatedly shows up in your list of "keeper" articles?   Find out what other documents 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 them as well.
    
3. Citation Search
   For the most important documents you found, use citation searching to find even more related items:
    
   1. 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.
       
   2. Go forwards in time by finding the articles (using Scopus and Google Scholar) that cite this document.
      You'll discover how this item affected future research, even in areas not covered by your subject search.  
       
   3.  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.

Would you like to see the literature research process used in real-life problem solving?  

Kirkwood, Patricia Elaine and Parker-Gibson, Necia. Informing Chemical Engineering Decisions with Data, Research, and Government Resources.  Morgan & Claypool, 2013.  Synthesis Lectures on Chemical Engineering and Biochemical Engineering #1. 

Chapter 7: Case Study 1: Finding a More Ecologically Friendly Plastic for Product
Chapter 8: Case Study 2: Biofuels: Using (Mainly) Governmental Resources to Inform Your Decisions

The case studies are in the chemical and agricultural engineering fields but the basic concepts and techniques used could apply to all areas of engineering.  Kirkwood and Parker-Gibson do not use the PICO formula per se but you can easily see those concepts in their research questions. Take note of how in both cases background material applicable to the research question was gathered first before searching literature databases for articles, etc.  You'll also see how decisions were made on which terms to use in the search statements and how the search was refined as information was found. 

Also note, that when doing a literature review for problem solving, there maybe more than one PICO question or more than one informational need to the problem.   This contrasts with academic research in which you may be investigating a single question or aspect of a topic.