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In-depth search strategies

Systematic searching and chain searching are two strategies for information retrieval that you might use for instance for finding earlier research for a literature review. In systematic searching you go through a search process several times. Chain searching means that you start from already available sources in order to find more material.

Go deeper and find more

When writing an essay or a dissertation you might need to dig deeply into the research in your subject area. For a comprehensive result you may make use of in-depth strategies for information searching. On this page we describe the search strategies systematic searching and chain searching.

Search systematically to map research

In a systematic search you follow several different steps in a search process, which is then repeated until you judge that you have finished. Searching in such a structured manner enables you, for instance, to map previously published research in your subject field.

The different steps of the search process

Searching for information is a process where different elements interact with each other. Follow these steps for a systematic search.

Start from your purpose and research question

Start from your purpose and your research question when searching. Your research question affects the search process – if it is too broad, too narrow, or unclear it might be difficult to find material.

You might need to modify your purpose and research question while you are searching for information. This is a natural part of the search process.

Select search terms

Before starting your search you need to consider which of the words in your research question are most important and carry most meaning. These keywords will form the basis for your search. Then find synonyms for your keywords to increase the number of search terms you can use.

In the majority of research areas you get better hits if you search in English. A research question like "How does the electoral system influence female representation in the UK House of Commons?" might for instance generate the following English search terms:

  • election system, electoral system, voting system
  • Great Britain, United Kingdom, UK
  • representation
  • women, females
  • House of Commons.

A list of subject terms (thesaurus) – an integral part of some databases – is another aid to finding good search terms. Lists of subject terms can help you

  • find relevant terms within your subject
  • find relevant English terms.

Carry out your search in relevant databases

Once you have established your search terms it is time to start searching. Select a few databases or search tools that are relevant to your subject.

The database list in the library search tool shows you which databases exist in a particular subject:


Your search will be more effective if you use various search strategies, such as

  • using AND to make your search narrower
  • searching more broadly by writing OR between synonyms
  • keeping composite concepts together using quotation marks
  • using an asterisk (*) to include all endings of a word
  • combining several different search terms and synonyms with the help of parentheses (creating search strings).

Sample search string: ("election system" OR "electoral system" OR "voting system") AND ("Great Britain" OR "United Kingdom" OR UK) AND representation AND (women* OR female*) AND "House of Commons"

Many databases and search tools also include filter functions which can make it easier for you to find relevant material.

Here you can find further reading and videos about basic search techniques:

Basic search techniques

Document your searches

Make notes of your searches in the course of the search:

  • the databases you use
  • the search terms you are trying out
  • how you combine the search terms
  • the filters you apply
  • the date the search was carried out.

This saves time for yourself, and you can also tell other people how you have carried out your searches.

If you do a literature review as your degree project you might be required to provide detailed documentation of your searches.

Examine the result of your search

Once you have carried out your search it is important to examine the result:

  • Did you get hits that are relevant to your research question?
  • Are you getting too many or too few hits?
  • What aspects of your search worked well and less well?

Take a closer look at your hits and see if you can identify new keywords. You might for instance look at the subject terms, abstract and full text of the hits.

Also remember to evaluate how credible the hits are. In many databases it is possible to single out hits from scholarly journals via filters such as "peer review". However, it is always up to you to assess whether a source is or is not scientific.

Scholarly publications

Evaluation of sources

Save information about your sources for the reference list

When you have found good sources that you want to use in your work it can be a great help if you save the data for your reference list in a systematic manner.

To facilitate working with references you can use reference management software or functions available in databases to create ready-made references. When you save and create references in this way it is important always to check that all necessary information about the source is included and that the reference is correct in terms of the reference system you use.

Here you will find more information about references and reference management software:

Writing references

Software for writing references

Adjust and repeat until you are satisfied

Think about how you might adjust your search terms and your search to get hits that are as relevant as possible. Information searching is a process in which you have to repeat searches and finetune them based on the hits you get from each search. Then carry out new searches incorporating new terms that you have generated during the process.

Often you also have to return to other steps within the search process:

  • Do you need to finetune your research question?
  • Could you try searching in another database to get better hits for your specific subject?
  • Might you try another search technique to get more or fewer hits?

Continue adjusting your searches until you judge that you have carried out a sufficiently extensive mapping of the research within your subject field.

Enhance your knowledge about systematic searching

If you need to know more about systematic searching we recommend two guides from the Karolinska Institute University Library (KIB). One is aimed at students and the other at researchers and doctoral students.

Structured literature reviews – A guide for students

Systematic reviews

Films about systematic searching

Search terms and search questions - get to know your topic

Explore your query and find keywords to get a better search result.

Pick out keywords from your search question

We show examples of how to identify keywords in different search questions.

Put your search terms into groups

Make groups of keywords and synonyms for each concept in your search question.

Find more sources using chain searching

If you have already found, or been recommended, certain sources you might start with these in order to find other relevant literature. This search strategy is often called chain searching as you can regard the different sources as links in a chain. By following references from one relevant source to others you follow a kind of chain that leads you to more material.

Four tracks for finding more sources

Once you have identified your starting points there are several different ways for you to progress in your chain searching.

Use reference lists to find new sources

Going through reference lists in sources that you have already found could be a good way of finding new and interesting sources.

  • Start from books and articles recommended by your supervisor or experts within your subject area and check the reference lists to gather more sources.
  • You can also use the reference lists in your textbooks.
  • If certain sources are given particular prominence in your original sources it might be a good idea to examine these more closely.
  • Bear your research questions in mind when you assess whether a source is of interest to you. This will make your work more efficient when you are going through numerous long reference lists.

Search based on citations to find important sources

Check books and articles recommended by your supervisor or experts within your subject field. Have they been cited in other sources?

  • A source that cites your original source often deals with a similar subject. In this way you can use citations to find new and relevant material.
  • If a source has been cited many times this might be a sign that the article is important within its field, but it could also be because other researchers are criticising the article.
  • Citation-based searching is a strategy that you can use to identify important or controversial publications.

Large databases such as Google Scholar, Scopus, Web of Science and certain subject specific databases have good tools for calculating the number of citations a publication has generated.

Find new sources in review articles

A review article is a summary of a certain research area produced by one or several researchers. The review article also lists key sources and researchers.

Try finding up-to-date review articles so as to include the latest research within your subject. Large databases such as Scopus, Web of Science and PubMed include good tools for filtering out review articles.

Pay attention to references while reading

When you start reading to familiarise yourself with your subject, it is a good idea to pay attention to whether certain researchers and sources frequently reoccur in the literature. If a source is cited in several other sources this could be a sign that it is important within your subject area.

Start searching in the search tool or databases

Learn more

Questions about information searching?

Do you feel lost among databases and scholarly publications? Visit our drop-in sessions or make an appointment for a tutorial and we will help you. You can also submit short questions via chat or the contact form or ask the staff at the information desk.

Latest update: 2022-08-31