When beginning a research project, one of the first steps you are likely to carry out is performing a literature search to obtain an overview of the current state of the field. Performing a literature search can help you understand what is currently known about a specific topic and what question or questions remain unanswered. If you did not perform a thorough literature search prior to beginning your research project, you may wish to do so later in the research timeline: for example, when writing the Background section for your paper or the introductory chapter to your thesis. A well-performed literature search is also critical when writing a review paper to ensure that you have adequately covered the state of the field and have not missed any important or relevant papers.
How to search for relevant articles on a topic
The first step in performing a literature search is to generate a list of keywords related to the main theme that you are interested in exploring. These keywords should ideally be specific enough to retrieve a reasonable number of hits, without being so specific that they unintentionally exclude relevant papers. For researchers in the biomedical fields, MeSH terms are an invaluable resource for designing an appropriate search strategy. MeSH terms, or medical subject headings, are the National Library of Medicine (NLM)’s curated vocabulary list that is used to index and search for publications in the biomedical sciences. Using MeSH terms to search PubMed eliminates the possibility of overlooking potentially relevant search results by neglecting to include different word endings, plural or singular forms, or synonymous terms, as these variations are already incorporated within the established terms. MeSH searches also offer the opportunity to further narrow down a search by subheadings and/or whether the search term is the major focus of the papers retrieved. For more information, as well as tutorials on how to use this powerful search tool, visit the NLM’s MeSH homepage.
PubMed also offers a variety of helpful tools for literature searches, such as the ability to set up an alert that will notify you when a new paper that corresponds to your search parameters appears in the database. To take advantage of this feature, you will need to create a PubMed account and be sure that you are logged in when performing a search. Specific searches (e.g. combinations of MeSH terms or other keywords) can then be saved, to be repeated at a later date or set up to correspond to an alert. We recommend visiting the PubMed help site for extensive tutorials on how to get the most out of this database and its integrated search tools.
Of course, there are a variety of databases other than PubMed that can be explored as part of your literature search, so it is important to identify which of these databases are most relevant to you and your research goals. Some of the most popular databases other than PubMed include Scopus, Web of Science, and GoogleScholar.
Keep in mind that most databases default to searching only English-language content, so if you are interested in retrieving papers published in other languages, be sure to specify this in your search parameters. Another useful feature that you can specify in your search parameters for most databases is whether to search the full text of articles, or only the title and abstract, which can help identify the most relevant papers if you are using fairly broad search terms.
How to identify and shortlist relevant articles on a topic
Once you have performed your initial literature search and are satisfied with the list of references that you have retrieved, the next step is to evaluate this list of potentially relevant papers in more detail to determine which are most pertinent to your topic of interest. We recommend beginning by reading the abstracts to rule out any papers that are not directly related to your research question or topic of interest. Even if the text of a paper contains the target search terms, the main focus of the paper may be an unrelated topic, so reading the abstracts can help rule out papers that will not ultimately be helpful to you.
In addition to reading through the abstract, it can be helpful to briefly asses the timeliness of each of the papers retrieved by your initial search to see when they were published. Papers that were published more recently are more likely to contain important information related to your study or manuscript than those that were published earlier, especially in fields where research is progressing rapidly. Of course, there are some exceptions to this rule, such as in the case of landmark or groundbreaking papers, which are often important for their historical value. In most situations, however, the more contemporary a paper is, the more relevant it will be to the current state of the field.
Another useful strategy for creating a strong, targeted shortlist of papers is to read relevant review papers in full and consult their reference lists carefully. If your search strategy was well-designed, then ideally you will already have retrieved many, if not all, of the papers cited in a closely related review article. Even so, it can be very valuable to read through these types of articles closely in case the authors highlight other aspects of the topic that you may have neglected to include, or cite papers you may have overlooked that could be useful for your purposes.
There are a number of online tools that can help you further identify and shortlist papers that are relevant to your topic. For example, when you access an individual article record in PubMed, the database automatically generates two lists of related papers: those that are cited in the paper you are looking at, and those that the paper you are looking at cites. This can be an excellent way to identify closely related publications. You could also consider using add-on tools such as the internet browser extension LazyScholar, which, among other features, provides recommendations of new and related papers you may be interested in based on the paper that you are currently viewing in your browser window.
How to save and organise citations
Once you have curated your initial search results into a shortlist containing only the most relevant and interesting papers, you will want to organise them in a way that makes them easy to find and use when planning your project or writing your manuscript.
If you have access to a reference management tool such as Mendeley, Zotero, or EndNote, this is one of the best ways to organise a collection of papers. All reference management tools can be used to record references to a collection of papers, and many also offer an option to store full texts of papers in PDF format.
You can also store downloaded papers on your computer or using a cloud service like Dropbox (which is particularly useful if you want to share a collection of papers with other users). If you plan on storing your papers this way, we recommend developing an organisational strategy that will help you easily identify and retrieve specific papers when needed. For example, you may wish to consider:
- Developing a file name strategy that makes it easy for you to identify a specific paper. This could include the first author’s last name, the year of publication, the journal name, and perhaps one or more keywords, e.g. ‘Aunkul_2002_JAMA_glycemia’.
- Creating an ‘index’ file that includes these file names associated with brief summaries of each paper. These summaries should ideally highlight the most important features of each paper with regards to your topic, and can contain short notes on the specific ways in which the paper relates to your research.
- Organising all of the papers on your shortlist into subcategories or subfolders based on topic; grouping similar papers together can make them easier to find and retrieve when needed.
If you are looking for a less manual way to store and organise your papers, consider using a tool like PaperPile, which was designed to work with Chrome and Google apps. This browser extension enables you to bookmark references while browsing, store PDFs in Google Drive, and insert references into manuscripts written in Google Docs. Another option is to use built-in database tools like Google Scholar’s ‘my library’ feature, which enables you to quickly and easily save references found during a Google Scholar search.
In summary, using the right tools and strategies can help you perform a thorough, well-designed literature search and ensure that you are well-informed and well-prepared to start designing your project or writing your paper.