Searching is part know-how of techniques and part discipline-specific practices. On this page we present some search examples from different disciplines and one for a systematic review. Here you will find search examples from
Some of the examples below are tied to using specific databases, while others show more of the search process and how to think about your topic and choose different databases or approaches. Experiment with the examples to become familiar with the various strategies for efficient searching.
Research statement: Heros’ and villains’ use of alcohol and tobacco in Disney animated films 1937-2000
With research projects in the humanities, it is not a question of using only one search strategy or only using one place to search. In this case it is useful to divide the research statement into components and search literature for each component seperately.
Not every aspect of relevance to the project is always evident in the research statement. In this case, there could be an interest in how children’s exposure to substance use through popular culture affects their health choices later in life, which would also entail finding research literature on this topic.
The literature used to inform a project like this would be found through various sources.
Research statement: Narrative effects of thematizing truth in German autobiographical fiction in the 20th century
When you search literature for a PhD in the humanities, you will always need more than one database and more than one search strategy. In this case, it would be useful to search for literature regarding the different components of the research statement separately.
Though it is not explicit in the research statement, you would also need to examine how the specific works of autobiographical fiction in your study were received when published and if there has been any previous research done on these works.
A PhD like this would require the use of many different types of literature and would therefore use several types of databases and catalogues to find the required literature. Of particular importance here would be to use reference tracing and possibly citation searches.
Research question: The effectiveness of light therapy interventions to treat winter depression.
Database: PubMed (Medline). Relevant in biomedicine, life sciences and social sciences.
Date of search: May 2013
Divide your search into several steps and combine results afterwards. When searching literature in medicine and health, make use of defined subject headings in MeSH.
Step 1: Searching for “winter depression”
The MeSH term for this is seasonal affective disorder. In Scandinavia this condition is commonly named winter depression, which is mentioned in a few abstracts. The terms are combined with OR, to retrieve articles where either is mentioned. The list below shows search terms and numbers of results in parentheses. Searches are marked with the hash symbol ( # ) in PubMed.
Search 1: seasonal affective disorder[MeSH Terms] 1039
Search 2: seasonal affective disorder[Title/Abstract] 976
Search 3: winter depression[Title/Abstract] 240
Search 4: #1 OR #2 OR #3 1414
Step 2: Searching for “light therapy interventions”
The correct MeSH term for light therapy intervention is phototherapy and this is combined with light therapy in the title and abstract as a synonym. Additional searches for the terms in titles or abstracts here add a few relevant articles. They are all combined with OR, to retrieve articles where either term is mentioned.
Search 5: phototherapy[MeSH Terms] 25680
Search 6: phototherapy[Title/Abstract] 4834
Search 7: light therapy[Title/Abstract] 1050
Search 8: #5 OR #6 OR #7 27496
Step 3: Combining search results
Finally, both sets of terms are combined with AND. This will retrieve a combination of the words above.
Search 9: #4 AND #8 656
Step 4: Limiting search results
Now you have 656 references to articles concerning your search terms. If you want to decrease that number further, you can limit by study design, for example to reviews, which will result in 131 studies
Search 10: (# 9) Filters: Review 131
An additional limit by publishing year will decrease the number even further. There are 42 reviews published in the last ten years.
Search 11: (# 9) Filters: Review; published in the last 10 years 42
For an initial check of relevance of the retrieved documents, browse titles, year of publication, contributing authors and journals involved. Keep revising your search strategy and also consider setting up an alert. As no database is exhaustive, consider including searches in other databases. Pubmed is often used for finding clinical information. If you plan a systematic review, we advise you to search MedLine (Ovid).
Research question: Symbiotic relationships between Lepiotaceaean fungi and leaf-cutter ants.
Database: BIOSIS Previews, which is a part of Web of Knowledge. Relevant for the life sciences.
Date of search: 10. January 2014
Divide your search into several steps, search separately for relevant keywords according to research topic, combine and refine afterwards.
Step 1: Searching for leaf cutter ants and Lepiotaceaea fungi
Make sure to include various spellings and relevant synonyms of a search term or search concept. In this case, Latin names as well as common names are combined in a Boolean OR search. Add a wildcard (here *) to the stem of a word to include all forms. In BIOSIS, searching by topic means searching by title, abstract or keywords. The list below shows search expressions and number of results in parentheses.
Search 1: Topic=(Atta or Acromyrmex or (leaf cutt* ant*) or (leafcutt* ant*)) (1529)
Search 2: Topic=(fungus or fungi or lepiotaceae*) (488401)
Step 2: Combining search results
Go to your search history and combine the previous two searches with the Boolean operator AND. Searches are marked with the hash symbol (#) in BIOSIS.
Search 3: #1 AND #2 (385)
Step 3: Refine results to type of work
The left panel in the result list of the search interface lets you refine your search. Reviews summarize previous research and may be a good starting point. Choose Literature Types and tick off Literature Review if you would like to start with the eight papers retrieved in our example.
Search 4: Refined by: Literature Types=(LITERATURE REVIEW) (8)
For our topic Symbiotic relationships between Lepiotaceae fungi and leaf-cutter ants, a total of 385 documents were retrieved (Step 2) using BIOSIS on 10 January 2014.
While it is tempting to include a third search concept, symbiosis, this would exclude the documents dealing with symbiosis but without mentioning it in the title, abstract or keywords. If a paper is about both fungi and ants, it is also likely to relate to symbiosis.
For an initial check of relevance of the retrieved documents, try browsing titles, year of publication, contributing authors and journals involved. As no database is exhaustive, consider including searches in other databases. Keep revising your search strategy and also consider setting up an alert.
Research question: The impact of having divorced parents on self-esteem in adolescents.
Database: PsycINFO (Ovid). Relevant for psychology, health sciences, social sciences and education.
Date of search: 6.January 2014
Divide your search into several steps. Identify the main concepts in your research question and search separately for relevant keywords for each concept. In our example we take self-esteem, adolescent, and divorced parents to be the main concepts. Individual searches are then combined. You can then consider using various possibilities to refine your search result.
Step 1: Searching for “self-esteem”
Make sure to include various spellings and relevant synonyms of a search term or search concept. Check the thesaurus for possible subject headings that match your main search terms well enough to be included as search criteria. The thesaurus of a database may not have a subject heading that corresponds with your free text search terms. You will then need to consider whether or not it would be meaningful to include any of the options available options in your search. In PsycINFO, a subject heading search will be marked with a slash (/) in the search history. Recall your search history to see the individual searches representing the main concept, “self-esteem”, and combine them using the Boolean operator OR. The list below shows spelling variants of “self-esteem” and the numbers of results in parentheses.
Search 1: self-esteem.ti,ab. (33648)
Search 2: selfesteem.ti,ab. (51)
Search 3: self esteem/ (20666)
Search 4: Search 1 OR Search 2 OR Search 3 (37436)
Step 2: Searching for adolescents
Truncating after the ‘n’ in adolescen* will include adolescent, adolescents and adolescence. Truncating after the ‘n’ in teen* will include teens*, teen-ager/-s and teenager/-s.
Search 5: adolescen*.ti,ab. (160146)
Search 6: teen*.ti,ab. (15288)
Search 7: adolescent development/ (30756)
Search 8: Search 5 OR Search 6 or Search 7 (171826)
Step 3: Searching for divorced parents
Truncating after the ‘e’ in divorce* will include divorced (and therefore also “divorced parents” and “parents who are divorced”). Including terms other than divorce might be a good idea if it is not an important point that there has been a marriage before the break-up of the parents’ relationship. Remember to use quotation marks to delimit a compound search term. PsycINFO allows for truncation within a compound search term, such as “parent* breakup” which will include parental breakup, parents breakup and parent breakup. The searches representing the concept of “divorce” are combined with OR (Search 14).
Search 9: divorce*.ti,ab. (14081)
Search 10: “broken home*”.ti,ab. (503)
Search 11: “parent* breakup”.ti,ab. (7)
Search 12: “parent* break-up”.ti,ab. (9)
Search 13: divorce/ (7164)
Search 14: Search 9 OR Search 10 OR Search 11 OR Search 12 OR Search 13 (15255)
Step 4: Combining search results
Go to your search history and combine previous searches with the Boolean operator AND.
Search 15: Search 4 AND Search 8 AND Search 14 (94)
Step 5: Refining results to type of work
You can refine your search by choosing Additional Limits. If, for example, you want to identify the reviews among your search results, choose Methodology and mark the following options: 0800 Literature Review, 0830 Systematic Review and 1200 Meta Analysis. Limiting our research question by these types of applied methodology returns two documents.
Search 16: limit 15 to (0800 literature review or 0830 systematic review or 1200 meta analysis) (2)
For our research question “The impact of having divorced parents on self-esteem in adolescents”, a total of 94 documents were retrieved (Step 4) using PsycINFO on 06 January 2014. For an initial check of relevance of the retrieved documents, try browsing titles, year of publication, contributing authors and journals involved. Keep revising your search strategy and also consider setting up an alert. As no database is exhaustive, consider including searches in other databases.
When working with systematic reviews, the search is an important part of the method and needs to be conducted according to specific criteria. The search will provide the data set for the investigation undertaken in the review. Documentation of the search will published with the review.
Preparing the literature retrieval process is crucial, as this will be the foundation for your further work.
In searching, we distinguish between text words and subject headings, which are in different searchable fields of a reference. Text words (also called free text) are an author’s own written words that appear in the title and abstract. Subject headings describe the content of an article and are added by the database providers; these are often standardized.
Strategies for finding search terms
||Tobacco Smoke Pollution||Passive smoking|
|Vaporizers||Nebulizers and Vaporizers||Vaporization|
This example shows subject headings in Medline (which uses MeSH) and Embase (which uses Emtree), using different terms to describe the same concepts.
|women AND pregnancy||No need to search for women as only
women get pregnant.
|pregnancy AND preeclampsia
||No need to search for pregnancy as
preeclampsia only occurs in pregnancy.
The PRESS checklist (Peer Review of Electronic Search Strategies) has been developed to identify elements of accuracy of literature searches.
The precise way to build up a search strategy will depend on the researcher and on the database. Here we present an example of how the process of developing a search strategy can look and how the literature searches will look in different databases.
In the following, our research question is: Does exposure to smoke from e-cigarettes increase the risk of obstructive lung disease?
In this example, we will search PubMed, Embase and Web of Science. In a real-life systematic review on the topic, we would search more databases.
The main elements of this question are
To search as thoroughly as possible we need all the terms describing these elements. To systematize this work, all the words are organized in the table below.
|Electronic cigarettes||-Electronic Cigarettes||-electronic cigarette||-electronic cigaret*
|Vaporizers and tobacco smoking||-Nebulizers and Vaporizers
-Tobacco Use Cessation Products
– smoking cessation
– smoking cessation program
|Passive smoking||-Inhalation Exposure
-Tobacco Smoke Pollution
|– passive smoking
|– passive smoking
– tobacco Smoke pollution
– second hand smoking
|Lung disease||– Asthma
-Pulmonary Disease, Chronic Obstructive
– Lung Diseases, Obstructive
|– obstructive airway disease
– chronic obstructive lung disease
– obstructive pulmonary disease*
– obstructive airway disease*
– obstructive lung disease*
Date of searches: 6th October 2015.
Example PubMed search strategy
|#1||electronic cigarettes[MeSH Terms]||351|
|#2||electronic cigaret*[Title/Abstract] OR e-cigaret*[Title/Abstract] OR electronic nicotine[Title/Abstract] OR e-nicotine[Title/Abstract]||2299|
|#3||#1 OR #2||2332|
|#4||Nebulizers and Vaporizers[MeSH Terms]||8887|
|#5||vapor*[Title/Abstract] OR vapour*[Title/Abstract] OR vaper*[Title/Abstract] OR vaping[Title/Abstract] OR vaporizer*[Title/Abstract]||41836|
|#6||#4 OR #5||50309|
|#7||Tobacco products[MeSH Terms] OR Smoking[MeSH Terms] OR Tobacco Use Cessation Products[MeSH Terms] OR Tobacco use[MeSH Terms] OR Smoking cessation[MeSH Terms] OR Nicotine[MeSH Terms]||149671|
|#8||smoking[Title/Abstract] OR nicotine[Title/Abstract] OR tobacco[Title/Abstract]||2327822|
|#9||#7 OR #8||238856|
|#10||#6 AND #9||946|
|#11||#3 OR #10||3059|
|#12||Inhalation Exposure[MeSH Term] OR Tobacco Smoke Pollution[MeSH Term]||17475|
|#13||passive[Title/Abstract] OR exposure[Title/Abstract] OR pollution[Title/Abstract] OR second-hand[Title/Abstract]||735510|
|#14||#12 OR #13||741069|
|#15||Asthma[MeSH Terms] OR Bronchitis[MeSH Terms] OR Lung Diseases, Obstructive[MeSH Terms] OR Pulmonary Disease, Chronic Obstructive[MeSH Terms]||178505|
|#16||Asthma[Title/Abstract] OR Bronchitis[Title/Abstract] OR COPD[Title/Abstract] OR obstructive pulmonary disease*[Title/Abstract] OR obstructive airway disease*[Title/Abstract] OR obstructive lung disease*[Title/Abstract]||174515|
|#17||#15 OR #16||230092|
|#18||#11 AND #14 AND #17||77|
Example Embase Ovid search strategy
(Electronic cigaret* or E-cigarette* or electronic nicotine or e-nicotine).tw.
1 or 2
(vapor* or vapour* or vaper* or vaping or vaporizer*).tw.
4 OR 5
Smoking/ or smoking cessation/ or smoking cessation program/ or nicotine/
(Tobacco or Nicotine or Smoke or Smoking).tw.
|9||7 OR 8||407264|
|10||6 AND 9||1264|
|11||3 OR 10||2517|
passive smoking/ or exposure/
(passive or pollution or second-hand or exposure).tw.
|14||12 OR 13||964912|
obstructive airway disease/ or asthma/ or bronchitis/ or chronic obstructive lung disease/
(asthma or COPD or obstructive pulmonary disease* or obstructive airway disease* or obstructive lung disease*).tw.
|17||15 OR 16||342694|
|18||11 AND 14 AND 17||123|
Note: The / indicates a subject heading from Emtree and .tw. indicates text words.
Example Web of Science search strategy
|1||TOPIC: (e-cigarette* OR Electronic Cigarette* electronic nicotine OR e-nicotine)||973|
|TOPIC: ((vapour* OR vaper* OR vaping OR vaporizer*) and (tobacco product* OR smoking OR Tobacco Use Cessation Product*s OR tobacco use OR smoking cessation OR nicotine))||357|
|3||TOPIC: (Tobacco Smoke Pollution OR second hand OR exposure OR passive)||995 886|
|4||TOPIC: (Asthma OR bronchitis OR COPD OR (obstructive pulmonary disease*) OR (obstructive airway disease*) OR (obstructive lung disease*))||199 043|
|5||1 OR 2||1258|
|6||3 AND 4 AND 5||35|
Note: Web of Science does not have a subject heading index, therefore all search terms are text words.
While searching multiple databases, importing the result to a reference management program can help you create an efficient workflow. The reference manager can remove duplicate references, help you sort relevant references and organize your further work.
Documentation of the search makes your research reproducible and indicates that your methodology is sound. You would want to describe the search strategy that led to the included studies.
Check the journals’ instructions for authors for any specific requirements on how to report the search strategy. It can also be a good idea to look at published reviews in your preferred journal to see what is customary. For instance, some journals encourage the full search strategy in an appendix.
Documenting the search strategies can be done by:
Example on how documentation can be done in a section of an article
Studies included in this review were located from searching PubMed, Embase Ovid and Web of Science (last search 6th October 2015). The literature search included MeSH-terms and text words in the following combination: electronic cigarettes or tobacco vaporizers and tobacco exposure and obstructive lung diseases. The full search strategy in PubMed included the following MeSH-terms and text words: (electronic cigarettes[MeSH Terms] OR electronic cigaret* OR e-cigaret* OR electronic nicotine) OR ((Nebulizers and Vaporizers[MeSH Terms] OR vapor* OR vapour* OR vaper* OR vaping OR vaporizer*) AND (Tobacco products[MeSH Terms] OR Smoking[MeSH Terms] OR Tobacco Use Cessation Products[MeSH Terms] OR Tobacco use[MeSH Terms] OR Smoking cessation[MeSH Terms] OR Nicotine[MeSH Terms] OR smoking OR nicotine ))) AND (Inhalation Exposure[MeSH Term] OR Tobacco Smoke Pollution[MeSH Term] OR passive OR exposure OR pollution OR second hand) AND (Asthma[MeSH Terms] OR Bronchitis[MeSH Terms] OR Pulmonary Disease, Chronic Obstructive[MeSH Terms] or Asthma OR Bronchitis OR Chronic Obstructive Pulmonary Disease* OR COPD OR Obstructive pulmonary disease* OR Chronic Obstructive airway Disease* OR Obstructive airway disease* ).
The search was adapted to Embase with the following Emtree terms: electronic cigarette, vaporization, smoking, exposure, obstructive airway disease, asthma, bronchitis and chronic obstructive lung disease, and to Web of Science by searching by topic. There were no restrictions on language or publication dates. The reference lists of the included articles were screened for additional references.
For further input and advice on systematic searching, consult your library, help pages in databases and literature on the topic. Some libraries offer courses in systematic searching, or they will do such searches on request.
Haraldstad, A. M., & Christophersen, E. (2015). Literature searches and reference management. In P. Laake, H. B. Benestad, & B. R. Olsen (Eds.), Research in medical and biological sciences from planning and preparation to grant application and publication (pp. 125–166). Amsterdam: Elsevier.
Higgins, J. P. T., Green, S., & Cochrane, C. (2008). Cochrane handbook for systematic reviews of interventions. Chichester: Wiley-Blackwell.