There are different methods available to identify research relevant to your PhD-project. The type of literature you need will probably change throughout your research. It is common to explore the field in the beginning to get an overview. As the project evolves, the need for literature will be more specific and your searching will be more targeted. Different features in the literature databases will support these different approaches.
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Before you start searching for literature, you have to consider where to search, and that decision should be based upon where the research in your field gets published; is it in books, reports, articles or in other publication types? This will determine whether you should search the library catalogue for books, subject-specific databases for research published as journal articles, or organisations’ websites for reports. If there is a subject-specific database in your field, this will retrieve a more specific search result than an interdisciplinary database. Some fields require that you search in more than one database to retrieve all relevant literature.
As a PhD student you have access to a research library. It will be useful to get to know the library and which services they can provide, for instance reference services, courses and guidance in literature searching, and reference management. Find out how you get access to their journals, e-books, databases and how you search their catalogue. The most common way to get electronic access to the library is by connecting with the university IP address. If you often work from home or are travelling, check if you can use VPN, remote desktop or other services for accessing the library.
Here we provide you with direct links to the collection of databases that your institutions have access to. The lists of databases are organised both alphabetically and by subject. Remember that you have to be connected to your university IP address to access the databases, and if you need personal assistance, contact your local library.
“Google Books can sometimes be very useful. You don’t get the entire book but you get a number of pages. It can be extremely useful if you don’t need the book that much but you want a general idea about what it is about”.
PhD, social sciences
In order to do an extensive search in any database, you must be familiar with the search functionality of the database in question. When it comes to searching by content, there are two ways of searching databases:
In case of metadata, the information in references is structured in different fields, which makes it possible to search specifically by:
Criteria for inclusion or exclusion may also be used in the searches, applied as limitations. This would commonly be:
The content, record structure, searchable fields and searching facilities will vary between databases, so always read through the help function. However, there are some features that are frequently used, here we will present a selection of them.
A full text search means that you search in the actual text of the article or book, and not just the reference or abstract which is more common. You have to match the terminology used by the author. Utilising technical search features will ease your searching (singular/ plural, spelling differences, etc.) since it can be hard to match the exact phrases used in the text.
Keywords are added to the article by the author and give you an impression of what the article is about. In most databases, you can narrow your search to these. Authors may use different terminology to describe the same concept, so think about relevant synonyms when searching.
Some subject-specific databases have a system of controlled vocabulary which makes searching easier. A thesaurus describes the content of articles in the same way as keywords, but this is added by a team of trained indexers and not the author. A thesaurus is useful since you do not have to take synonyms or spelling mistakes into consideration.
Examples of databases that include a thesaurus are:
In this section we present some examples of how searching in different databases can be done, with comments. Click on the examples to take a closer look.
Problem: The impact of divorced parents on self-esteem and self-image in adolescents.
Database: PsycINFO (Ovid). Relevant in psychology, health sciences, education, social sciences etc.
Problem: Differences of the fungi Lepiotaceae living in symbiotic relationship with leaf-cutter ants.
Database: Web of Science. Relevant in all fields.
Problem: The effectiveness of light therapy interventions to treat winter depression.
Database: PubMed. Relevant in biomedicine, life sciences and social sciences.
One way of keeping up to date in research is to keep track of what key researchers publish and who is citing whom. To get citations from specific authors, you can limit your search to author name only.
Authors are mostly registered in the databases with their last name and initials. Sometimes the first name is included but this will vary between databases. If you check the help function in the given database, your searching will be more precise. Some databases have author indexes where it is possible to pick the exact author you need, based on their affiliation.
If the author has different variations of his or her name, or e.g. two last names, it could be a good idea to search for all variations of the name if retrieving all citations is your goal. The Nordic letters Æ, Ø, Å, Ö, Ä can be tricky in English databases. Some databases can handle them, otherwise they are often replaced by A and O.
Remember that an author may be the subject of a discussion, and their name could appear in the title or abstract of an article.
“I use bibliographies of other books a lot. If I have a good book that is related to what I’m doing, then I always carefully read the bibliographies”.
PhD, social sciences
Looking forward in citations is a way of following a development or a debate in a research area. Databases such as Web of Science and Google Scholar have a “Cited by” tool, where you can find out how many times the article in question has been cited and by whom. How many times an article is cited can reveal something about its impact. It may be an idea to check the citations in different databases, since “Cited by” is counted within each database.
Example: “Times Cited” and “Cited References” in Web of Science. This shows the references this article is built upon and the articles where this one is cited.
To keep up to date with the most recently published information and developments, you can follow cited works and trace citations by subscribing to current awareness tools in databases and in journals. A selection of current awareness services is outlined below.
This section presents some more advanced features concerning searching.
Combining searches with Boolean logic
The use of AND, OR and NOT, called Boolean logic, helps you to combine your search words in the correct logical way.
- Combining with AND will retrieve a search result with all your search words combined.
Example: influenza AND vitamin C
- Combining with OR will retrieve at least one of your search terms, and up to as many terms as you have included. This is useful when you have synonyms as search terms and are interested in either of the words.
Example: influenza OR common cold
- Combining with NOT will exclude search words from your result. Use this with great caution, as you do not necessarily have control of what is excluded from the result.
Example: common cold NOT vitamin C
In addition, you can combine search words utilising AND and OR. Here each set of search words is searched individually, and then they are all combined to retrieve literature concerning e.g. treatment of common cold.
1. influenza OR common cold
2. vitamin C OR garlic OR antibiotics
3. 1 AND 2
Truncation helps you find an alternative or an open ending to your search word. This is useful when you search for several words with the same root or want to search for both the singular and plural form of a word. This is one of the most common features in databases. Use the database’s help site for verification of the correct symbol. The most common symbols are *,?, #, $.
Example: child* matches children, child, childhood, childish
Some databases allow you to use a truncation sign at the beginning of the word to include variations.
Example: *oxide matches peroxide, sulphoxide, nitroxide.
Wildcard replaces one character in your search word. This is useful e.g. when there is a different spelling between British and American English.
Example: Colo?r matches both color and colour
By enclosing your search terms together with Boolean logic or proximity operators in parentheses you can decide what should be interpreted together. Words within parentheses are read first, and then the words outside the parentheses.
Example: ((common cold) OR influenza) AND (garlic OR vitamin* OR (Antiviral treatment))
When you search for a specific phrase, enclose them with double quotation marks (“…”) to narrow the search to those words in that specific order.
Examples: “United Nations”, “breast cancer”
Some databases help you search for words that are close to each other. Here we provide you with some examples:
Web of Science
NEAR = Near operator. Add a number to define how many words you want to search within.
Example: tax NEAR/5 reform, finds records containing the words tax and reform within five words of each other.
N = Near operator. Retrieves records with the words regardless of the order in which they appear. Add a number to define how many words you want to search within.
Example: tax N5 reform, finds records containing the words tax reform as well as reform of income tax.
W = Within Operator. Retrieves records with the words in the order you entered them. Add a number to define how many words you want to search within.
Example: tax W8 reform, finds records containing tax reform but not reform of income tax.
ADJ = Adjacent operator. Retrieves records with the words regardless of the order in which they appear. Add a number to define how many words you want to search within.
Example: tax ADJ4 reform, retrieves tax reform as well as reform of income tax.
Limit your search
Think about the possibility of limiting your search by study design, document type, language, year of publication etc. This may help you get closer to what you are looking for.
If you need personal assistance in searching, contact the library at your institution.