The Mad Engineer Blog
The single most important thing to starting a research project is knowing what has already been done by others. Yet students tend to shy away from doing a literature review. Granted, reviewing the literature can be a daunting task. There are hundreds if not thousands of papers written on a topic. Where do you begin?
In this post, I will show how to use databases to search for references, organize references in a reference manager like EndNote, sort through titles and abstracts to find relevant papers, and search papers for additional references to add to your personal library. Keep in mind that a literature review is an ongoing task. You should always be on the lookout for new papers that aren't already in your library.
If we know the names of journals that publish papers on the topic we are researching, we can search those journals directly. But we may not know which journals are most relevant if we are working in a new field. In addition, if we only search specific journals, we might overlook important papers that were published elsewhere.
So we use databases to search large numbers of journals. Students like to default to Google Scholar because it is familiar, but there are much better databases for academic research and to access them you need to go through your library.
For engineering, I like ProQuest because it covers a lot of territory, including the Elsevier and Springer journals. Depending on what I'm researching, I may also search the ASCE database. This is because ASCE has its own library and won't turn up in other databases. To figure out which databases cover a field, you can ask your librarian or search the library's website.
To access the ProQuest database, I go to lib.umich.edu and search "proquest." ProQuest shows up under databases. I click the link to access ProQuest. I am prompted to enter my university credentials.
Once you have settled on a database (or databases), you need to figure out your keywords. The broader your search terms, the more results will be returned in your search. If your search is too narrow, you will miss a lot of important and relevant literature. I find choosing keywords to be an iterative process.
The other thing you should think about is where those keywords appear. In most cases, you can limit your search to keywords appearing in the title and abstract, for example. If you search anywhere for the keywords, you will get papers that just have a keyword appear once in the whole article.
Let's search for papers related to wildfire policy that were published in the last ten years. If I enter "wildfire AND policy" in the database for a period covering the last ten years (i.e., "PD(2011-2022)"), I get more than 100,000 results. The search is too broad and probably returns a lot of irrelevant results.
We can limit the results to peer-reviewed articles, which brings the number down to 11,000. Peer-reviewed means that the papers were rigorously evaluated by the authors' peers in the publishing process. Peer-reviewed papers carry a lot more weight than those not subject to peer review because the findings were presumably scrutinized very closely prior to publication.
Note that these results are searching anywhere in the document for the keywords. We can narrow our search even further by requiring the keywords to appear in the title or abstract by searching the following: "AB,TI(wildfire AND policy)". This returns a little more than a thousand papers, which is a lot more manageable.
Note that our search isn't necessarily done. We may need to consider alternative keywords. For our search on wildfire policy, we may need to also search for "wildland fire," “forest fire,” “brush fire,” and "bushfire" to accurately capture the whole field. In addition, we can't forget that there are other databases we may want to consider. In this case, we might want to consider a database like JSTOR that searches social science journals in addition to ProQuest.
Exporting Search Results
You can usually save your results in ProQuest or in other databases, but I prefer to have everything in one location. This is where having a reference management system comes into play. I use EndNote, but others may prefer Mendeley or Zotero due to cost savings and other features. Regardless of which software you use, you can usually export the results from a database search into your reference manager.
To export from ProQuest, you check the box next to the papers you want to export. Note that ProQuest will only allow you to export 500 references at a time. Once you've selected the papers, you click the button with the ellipse (three dots) for All Save Options. A window will appear that will allow you to save the results as an RIS file (i.e., an EndNote compatible file). You can then import the file into EndNote by double-clicking it. After importing, you have the bibliographic information, abstract, and hyperlink to each paper you have downloaded.
I like to place references in groups to keep them organized. For now, I place all the references I’ve downloaded into the Policy group. As I read them, I will create groups with more focused topics.
I also recommend going to Library → Find Duplicates to remove duplicate records. After deleting duplicate records in this case, the number of unique references drops to seven hundred.
Sorting through the Results
The only way to know what the papers are about is to read. Generally, I do a quick scan of titles and abstracts to see if the papers are relevant and to put them into groups with more focused topics. Papers that are highly interesting will be flagged to read in depth, whereas papers that are unrelated will be flagged as “do not read." An example of an irrelevant paper is shown below. From the title and abstract, you can clearly see that the paper has nothing to do with wildfires even though the words wildfire and policy appear in the abstract. I do not delete the record because it is possible to come up in another search later, and I don’t want to triage it again. Instead, I keep it in the "do not read" pile and delete any duplicates in the future.
Now it's time to sort through the seven hundred papers I've found. I'll share with you a tip that I use to organize the literature graphically, which is something I found necessary when I did the literature review for my Ph.D. dissertation. When organizing the literature, I create a concept map of the main topics. The concept map is dynamic until I've finished reading, meaning that I am constantly adding and rearranging topics until they make sense to me. A concept map allows me to visually organize the information so I can see the main topics and their relation to one another. Below is a concept map I created based on review papers I have recently read related to wildfires. I used a free web tool called Bubbl.us to create this one. It helps me to visualize all the information I take in during a literature review of a new topic and to identify gaps in the literature.
Reading with Openness
Your initial search will cover a lot of the literature, but you should always be on the lookout for papers to add to your library. Once you begin reading the journal papers, you should always scan the reference list for relevant papers. If a relevant paper is not already in your library, add it and flag it to be read. I call this reading with "openness" because the approach is inspired by qualitative methods of data analysis. This is a practice that should follow you your entire academic career.
A literature review is hard work. It is easy to get overwhelmed, but if you follow a systematic approach and keep everything organized in a reference manager, it is a lot more manageable. Keep in mind that your search should be broad but within reason. You may need to choose more than one database, and you may need to search multiple combinations of keywords. Downloading the references to your library is only half the battle. You will eventually need to read through the papers to get a true understanding of what the papers are about. In this article, we skimmed titles and abstracts, but the next step is to read the papers “in full.” I put “in full” in quotes because a lot of information can be gleaned from a paper by skimming. At the end of the day, your research will be better because it will be based on the current state of the art.