Library Skills
Introduction to advanced literature searching
Advanced search techniques can be used by anyone, but they are essential if you are a Postgraduate student, and many final year undergraduate students should also be using them. If you are unsure whether to use these techniques or not, please speak to your personal tutor or module lead.
Subject heading searching
Subject heading searches are different to keyword searches. A keyword search will search the entire record of a document (or title OR abstract if that is what you have specified) looking for any term or a closely related word, regardless of whether or not it fully describes the document's contents.
In contrast, when a document, such as an article, is added to a database, the cataloguer will assign specific terms to that document from a list of approved, standardised terms. These terms are often called subject headings - although, sometimes they can be refer to as MeSH headings, thesaurus terms or controlled vocabularies. These subject headings are clearly defined and will only be assigned to the document if they are relevant to the contents of the document in question.
Example of subject headings for a journal article:
| Article title | Subject headings |
| What makes a mobile app successful in supporting health behaviour change? |
Health promotion; Mobile applications; Behavioral changes; Motivation; Conceptual frameworks; Self-efficacy; Data security; Privacy and confidentiality |
When conducting a keyword search the term that you use may appear in the search results, but may not be the primary focus of the research - the resource just happens to mention the term. The resultant search results might fit your search, but might not be relevant to your topic.
Subject headings, on the other hand, are useful as you can search for the overarching subject heading, and simultaneously all the terms related to the main heading, meaning you capture all the alternative keywords linked to that concept. For example, a subject heading search for 'stroke' can also include types of cerebrovascular diseases, such as brain infarction, ischemic stroke, cerebral stroke etc. This will ensure that relevant keywords to your search are not overlooked.
The table highlights the strengths and weakness of using subject searching.
| Advantages of subject heading searching | Disadvantages of subject heading searching |
| It will find material on the same topic even when the material uses different terms and keywords. | Different databases use different subject heading systems, so headings will vary between databases. |
| It will focus your search and help to reduce the amount of irrelevant information. | Subject headings might not be immediately assigned to new articles - sometimes there is a time lag in the article being fully tagged. |
| It will reduce the likelihood of missing relevant information. | It is not as flexible as keyword searching, as it relies on having some prior knowledge of the topic and associated terminology. |
You will need start by finding the relevant subject headings related to your topic, as different databases may use different sets of subject headings.
To find prescribed subjects headings, conduct a keyword search using the appropriate subject headings search box, and then browse the list of subject headings to locate the most relevant ones for your topic.
Alternatively, you can run a simple keyword search on your topic first, then look at the results to find a few relevant articles. Each entry should display which subject headings have been assigned to these articles which you can then use to build your subject heading search.
Please watch these two videos in this order: 1) 'Subject heading search: finding your subject heading/s', and 2) 'Subject heading searching: checking subject heading definition and entry terms'. Find the videos here
Some databases have search builder that allows you to add subject headings to your search. You will need to replicate your keyword search with your subject heading search, and then add your keyword searches to your subject heading searches to create the most robust search for your area of research.
This replication of your keyword search is why it is important to check the definition and entry terms (the synonymous terms that are automatically covered by your chosen subject heading) for your subject heading. For example, If your keyword search was:
stroke OR cva OR "cerebrovascular accident"
in theory you would need to search for these three as subject terms as well. However, if we use Pubmed as an example, by checking the entry terms for 'stroke', we can see that the entry terms already include 'cerebrovascular accident' and CVA, so you don't have to search for these as separate subject headings:
Databases will often have help pages if you're not sure how they function with subject heading searching. CINAHL, for example, has instructions for subject heading searching. These instructions will also work with MEDLINE (EBSCOhost).
You can often 'explode' a subject heading so it will simultaneously search for the overarching concept and all the narrower terms underneath it in the hierarchy. This makes it easy to look for all related terms within a topic which may be missed in keyword searching, and is likely to increase your results. Please watch these two short videos in this order: 1) 'Subject heading searching: hierarchies and exploding your subject heading', and 2) 'Subject heading searching: adding your subject heading to your search'. Find the videos here.
An advanced search strategy should use a combination of keyword and subject heading searches. You should still search for each of your concepts separately, but for each concept do both a keyword and a subject heading search. An example structure for an advanced search using the PICO framework (without an outcome search) is below:
|
SEARCH NUMBER |
|
|
1 |
Keyword concept 1 |
|
2 |
Subject heading concept 1 |
|
3 |
1 OR 2 |
|
4 |
Keyword concept 2 |
|
5 |
Subject heading concept 2 |
|
6 |
4 OR 5 |
|
7 |
Keyword concept 3 |
|
8 |
Subject heading concept 3 |
|
9 |
7 OR 8 |
|
10 |
3 AND 6 AND 9 |
Ebsco Connect. (2018) What are major subject headings and minor subject headings? [Online] [Accessed on 15th July 2024] https://connect.ebsco.com/s/article/What-are-Major-Subject-Headings-and-Minor-Subject-Headings?language=en_US
Ebsco Connect. (2019) Using CINAHL/MeSH subject headings [Online] [Accessed on 15th July 2024] https://connect.ebsco.com/s/article/Using-CINAHL-MeSH-Headings?language=en_US
Massachusetts Institute of Technology Libraries. (no date) Database Search Tips: Keywords vs. subjects. [Online] [Accessed on 15th July 2024] https://libguides.mit.edu/c.php?g=175963&p=1160804
Proximity Searching
Proximity searching is an advanced search technique that allows you to find words or phrases that appear close to each other within a specified distance, in any order. It is a useful technique to use if you have a concept that is difficult to describe because there are many variations that you could use.
The proximity operator used is often "N" for NEAR (find terms within X words of each other in any order), but it does differ from database to database - see table below for help on which proximity operator to use in which database platform.
The number after the operator specifies the maximum number of words between the search terms. For example, (injury OR pain) N5 (“upper extremity” OR shoulder OR arm OR wrist) would find results where injury OR pain and “upper extremity” OR shoulder OR arm OR wrist appear within 5 words of each other. You may need to experiment with different numbers to find the most efficient proximity search for your needs.
It is important to remember that not all databases use proximity searching, and the syntax used differs between databases.
Proximity operators for different platforms:
| Platform / Database | Operator | Example |
|---|---|---|
| EBSCOhost | N | health N3 interprofessional |
| ProQuest | N/ | health N/3 interprofessional |
| Ovid | ADJ | health ADJ3 interprofessional |
| Cochrane | NEAR/ | health NEAR/3 interprofessional |
| Scopus | W/ | health W/3 interprofessional |
See here for a short video on 'proximity searching' for your database