Literature Searching Lesson

Effective literature searching can require a great deal of thought and effort. When you've performed a good search, you should be confident that you have found exactly what you wanted or that it does not exist. Mediocre searching can mean that you've missed things or you're left with results that weren't really what you wanted. A good literature search follows these steps:

1.     Question Analysis

·         Before you even start, think about what strategy will best answer your specific question.

·         Isolate specific concepts from in your question, and think of different ways to represent each of them.

·         Identify other issues that might limit the results you want, like date, language, type of article, etc.

2.     Choosing Where to Search

·         PubMed is the obvious choice, but UW does have access to many other health-related databases, one of which might be a better choice depending on your search.

·         CINAHL focuses more on nursing and allied health fields and indexes book chapters and books, as well as audiovisual materials and journal articles. PubMed only covers journal articles.

·         The HealthLinks website offers a well-curated selection of the resources UW has to offer.

3.     Precision vs. Recall

·         Your search method depends on what kind of search you are doing. We call the two main types precision and recall.

·         Precision searching is when you are looking for one really good article on a specific topic. You want to make sure everything you find is on topic, and don’t care if you’ve missed things. This is the type of searching you do when you need background or clinical information quickly.

·         Recall searching is when you want to make sure you have everything on a topic. In this type of searching, you’re willing to sort through results that may not be on topic to make sure that nothing was left out. This is the type of searching you do for a literature review or when thinking of a new paper.

·         One of the main ways you can narrow or broaden a search is through the use of Boolean logic. This is used in most search engines, and consists of using AND, OR, or NOT to link concepts together.

·         AND requires the database to only return articles with both terms specified on either side of the AND. This is a precision technique; it narrows your search.

·         OR lets the database return articles with either on the terms on either side of the OR. This is a recall technique; it broadens your search.

·         NOT prevents the database from returning any articles with the word following the NOT. I prefer not to use this technique, as it can frequently strip useful results. It is instead better to add terms with AND for greater specificity.

4.     Controlled Vocabulary vs. Key Words

·         Most databases have many options for ways to search. Most of what you currently do is probably key word searching, where the system tries to find a match in the title and abstract, or in full-text.

·         However, these databases also have options to use controlled vocabularies to search terms that professional indexers have assigned to them.

·         A controlled vocabulary is a specially built thesaurus that controls how a concept may be referred to. In everyday life, we could say a certain piece of furniture was a “couch,” “sofa,” “loveseat,” “divan,” or “davenport.” Having this many words for one thing makes searching very difficult and time-consuming. In a controlled vocabulary, we have chosen one term to refer to all of these things and bring them all together under a common heading. Even though an author might refer to something as a “sofa,” if the controlled vocabulary has chosen the term “couch,” that is how it will be listed.

·         PubMed uses MeSH, or Medical Subject Headings, to control medical terminology in the same way. There are often many ways of referring to a single phenomenon, and the standardization provided by MeSH allows you to find the preferred term instead of thinking of every synonym. Learn more about MeSH with this video tutorial:

·         Neither one of these approaches are perfect on their own. Good, thorough, searching uses both keywords and controlled vocabulary terms.

5.     Limits & Filters

·         Once you have built a search, it is often useful to limit the results in other ways.

·         Clicking on Limits, just above the search box in PubMed, allows you to specify what you prefer for dates, types of articles, languages, and research subjects, among others

·         The filters are available on the upper right-hand corner of the search results screen, and they allow you to choose articles by type of article and availability.

6.     Getting an Article

·         Once you have found an article that you want, you can often access it by clicking on the purple “Check for Full Text” button on the individual article page. If the button does not work, or if there is no button, it is still probable that you will be able to find the article.

·         You can search for journal titles in the main UW library catalog at If the catalog indicates that we have an e-subscription, you can click on the title to see if we hold the issue you’re interested in. If we do, the catalog will connect you to the holding database, but you may need to input the citation information again.

·         If we do not hold the title or the issues you want online, put in a Document Delivery request with the main UW Library at If we have it in print or another institution holds it, the librarians will scan the article and email it to you as a PDF in just a few days.

·         If you are having difficulties, please do not hesitate to contact me ( or the librarians at the main Health Sciences library. They have a full time reference desk and can always assist with searches or obtaining articles. Our library liaison is Amy Harper, and you can reach her here:


In conjunction with this, everyone is instructed to complete the excellent interactive tutorial that the NIH has put together for PubMed. It emphasizes some of the concepts here, explains PubMed-specific techniques in greater detail, and reinforces the lessons with short quizzes: