Searching the literature

Before you start searching for literature, you need a clear, well-formulated research question, or series of questions. Start by doing a a quick search of OneSearch to get a feel for the amount and type of literature you may find.

• Break down your research topic into separate concepts (each concept will be a separate set in your search)
• Establish your search terms for each set
• Decide on any limits to your search
• Set out your search strategy in a spreadsheet or table

The search terms or keywords will need to take account of:

• Broader and narrower terms. For instance, "Natural disasters" is a broad term and earthquakes, floods, hurricanes are narrower terms within "Natural disasters".
• Synonyms and near synonyms. Such as workers, employees, personnel.
• UK and US English. Spellings, variations in terminology.  For example, what the British call "mobile phones" are "cell phones" in the USA.
• Changes in terminology over time. For instance, "Manic depression" is now called "Bipolar disorder".

Also consider that the field you search in a database will affect the number of results you retrieve.

For example:

• All fields: Your keywords may appear in any field. This will return a high number of results.
• Title/abstract: If keywords appear in the title and abstract, the item is likely to be highly relevant. Relies on well written, descriptive titles and abstracts.
• Keyword: Searches for your keyword in the author supplied keywords.  
• Specific fields exist in each subject database, such as Tests & Measures (PsycINFO)

In many subject areas, especially psychology, health and medicine, you are expected to use the thesaurus or system of subject headings in the databases. These systems of subject headings are valuable because:

• They use consistent terminology.  So articles which talk about cancer or tumours or leukaemia will be mapped to the Medical Subject Heading [MESH] term Neoplasms.

• They have a tree structure.  So you can look up Neoplasms as a MESH term and you will see that if you explode the term you will search for all the cancers in one go.

• The subject headings chosen reflect what the article focuses on.  So an article of 8,000 words might be given 20 headings in MESH.

• If you already know of some good papers in your area (“citation pearls”), look them up in a database and see what subject headings have been applied.  They may help you construct your own search strategy.

• There's more about using a thesaurus in the database guides which you’ll find in the online help available within each database

• If you are expected to retrieve all the literature on your subject, you should use a combination of thesaurus terms and free text or keywords.  This is because (a) the most recent items may not be indexed yet; (b) the concept you are studying may not be in the thesaurus; (c) indexing changes over time; (d) errors in indexing do happen.

Ways in which you might limit your search

• By date. If a thorough review article in your area was published in 1998, you could reasonably focus on material published after 1997. Or if the legislation on your area changed in 2003, then you  want material published after the new legislation came into force.
• By country or area.  If you are only interested in particular countries, you can often limit your search by geographical area.
• By age group.  Many databases allow you to state that you only want material about (say) children or elderly people.
• Human/animal studies.  Particularly useful in medical/life sciences work.
• By language. Do you just want material in English?  However if you are doing a thorough or systematic review, you may find that there are useful articles written in foreign languages.  They will often have an abstract in English which gives useful insights, or you may need to get a key paper translated.
• By type of document. For instance, do you just need peer-reviewed articles?
• By field. Databases allocate the different elements of a record to a specific field.  You can then specify which field is to be searched for a particular term. This screens out irrelevant material - for instance if you want material by an author called London put London into the author field, so you avoid all the articles about the city.
• By methodology Do you just need quantitative studies? Or qualitative studies?  It is NOT enough to simply add "qualitative" or "quantitative" to your search terms.  The article may not mention the actual word. So to restrict your search to qualitative studies add in words for methods used in a qualitative study such as questionnaire* OR survey* OR interview* OR "focus group*" OR "case stud*" OR observ* OR "grounded theory" OR narrative OR thematic OR experienc* OR "content analysis" OR ethnolog* as well as Qualitative.