When you base your statements of other people’s work, it is important that you credit the author(s) by providing a citation and reference to their original work.
By citing correctly, you:
- • follow academic guidelines
- • acknowledge other people’s work
- • show that you have done a thorough literature search
- • help the reader to find the original sources
Plagiarism
If your citations and reference work are not done adequately, you can risk being accused of plagiarism. Plagiarism means that you present other people’s work, thoughts or results as your own. Plagiarism is not acceptable and can lead to examination failure and expulsion.
In principle, anything in your text that is based on information from another source needs a citation and reference to that specific source. A source can be a book, report, scientific article, documentary or something else. NB! Remember to be critical of your sources. Not all published material is good material.
What is common knowledge?
Generally, you do not need to provide references for information that is considered common knowledge (e.g. the freezing point of water). However, if you are not certain of whether you should provide a reference or not: do it anyway. It is better to be safe than sorry.
REMEMBER! Any conclusions coming from an original study should be cited.
Every source that you use should be mentioned at least twice in your text: once after the sentence to which the reference belongs (in-text citation), and once in your reference list.
In-text citations usually contain only author name(s) and publication year (sometimes also page number), while references in the reference list include all necessary details to find back to the original source: name of the author(s), publication year, title of the work, name of the journal (if the material is from a journal) etc.
Exactly how your in-text citations and reference list are structured, depends on your referencing style. Two common reference styles in natural sciences are Harvard (name-year style) and Vancouver (numerical style). Within these styles, journals might have their own specifics. Regardless of the style you decide to use, use the style consistently throughout your text.
Direct Citations vs. Indirect Citations
Both indirect citations and direct citations require an in-text citation and the full reference in the reference list.
Indirect citation is when you summarize someone else’s work with your own words. This is the type of citation you will use the most throughout your text. NB! Simply changing the order of some words in the original sentence is NOT using your own words.
Direct citation is when you cite someone else’s text word by word. This type of citations is much less commonly used. Direct citations are mostly relevant when it is important to use the exact same language as the original source (e.g. when you need to get a definition right). It is important that it is clear what is part of the citation and what is not, by for example using quotation marks and/or by using indentation or making a separate paragraph only containing the cited text (more common if the citation is long). Direct citations of written sources also typically include the page number, from which the citation was found.
See Søk & Skriv for more information.
Reference Style
Reference styles that follow an author-year format are typically called Harvard styles. The following examples are based on the Harvard-styled reference style in the journal “Ecology”. All example references are fictive.
In the main text (in-text citations)
In-text, the citation contains the surname of the author(s) and the publication year (and sometimes page number). Usually, the citation is given in parenthesis behind the statement they support:
“Terrestrial ecosystems are limited by nitrogen availability (Johnson, 2019).”
Only when it is important to specify which study supports your statement, you could consider presenting your statement as follows:
“The study by Johnson (2019) showed that most terrestrial ecosystems are limited by nitrogen availability.”
Note that the author now became part of the sentence, and thus moved outside of the parentheses.
Here are some examples of how you write the in-text citation depending on how many authors the source has:
| Number of authors | In-text reference | Example with parentheses |
| Source has one author | [1st author] [Year] | … limited by nitrogen availability (Johnson 2019). |
| Source has two authors | [1st author] and [2nd author] [Year] | … limited by nitrogen availability (Johnson and Turner 2018). |
| Source has more than two authors | [1st author] et al. [Year] | … limited by nitrogen availability (Johnson et al. 2017). |
NB! Note that other journals might list more than two authors before switching to et al. “et al.” is also often in italics
If you have multiple sources supporting the same statement, you can list the references after each other (here separated by a comma). Order the references by publication year, starting with the oldest:
“…limited by nitrogen availability (Johnson et al. 2017, Johnson and Turner 2018, Johnson 2019).”
In the reference list
When using the Harvard style, your reference list should be arranged by the last name of the 1st author in alphabetical order.
The following reference list is in the style used in the journal “Ecology”. The first four references are fictive articles and the fifth reference is a fictive book. Note that they include different information. If you want to learn more about how different sources are referenced in Harvard style, check out NTNU’s Harvard-examples .
Remember that details such as how to write author names, where to use commas and periods, and when to use italics and bold, may vary between journals.
Reference list example
- Allen, R. M., and V. Peterson. 2018. Phosphorus in freshwater. Journal of Fake Articles 1:20–34.
- Johnson, K. S., V. M. Turner, and R. M. Allen. 2017. Phosphorus and nitrogen in marine and terrestrial ecosystems.
- Journal of Reference Examples 35:342-350.
- Johnson, K. S., and V. M. Turner. 2018. Nitrogen availability limits terrestrial ecosystems. Example Reviews 3:345-363.
- Johnson, K. S. 2019. Terrestrial ecosystems – a review. Journal of Hypothetical Examples 45:34-47.
- Turner, V. M., and V. Peterson. 2001. Nutrients and ecosystems. Reference List Press, Bergen, Norway.
Suggestions on how to structure references when…
...two or more sources have the same first-author but different co-authors: In the reference list, these references can be listed by the last name of the 2nd author in alphabetical order.
...two or more sources have the same author(s), but are published different years: In the reference list these references can be listed by publication year, the oldest study first.
...two or more sources have the same author(s) and are published the same year: In-text you can label your references with a, b... like this: (Johnson, 2019a, Johnson 2019b), to separate them. The reference labelled a is usually the first if listed alphabetically going by title. In the reference list, you include the same labels and follow the same order.
In a numbered reference style, such as Vancouver, you give all your sources a number based on when they are referred to in your text. Furthermore, you list them in the same order in your reference list.
The following examples are based on Patrias K. (2007) Citing medicine: the NLM style guide for authors, editors, and publishers. 2nd ed. Wendling DL., technical editor. Bethesda (MD): National Library of Medicine (US). Available from: http://www.nlm.nih.gov/citingmedicine. All example references are fictive.
In the main text (in-text citations)
References are numbered in the numerical order they appear. The first reference in your text is labelled number 1, the second number 2 etc. If reference 1 supports a statement later in your text as well, it should still be referred to as reference 1. Write the number of your reference in parenthesis behind the statement it supports:
“Terrestrial ecosystems are limited by nitrogen availability (1).”
If you have multiple references supporting the same statement, for example reference 1, 2 and 3, you can write:
“… limited by nitrogen availability (1-3).”
Or if reference 1, 2, 3 and 5 supports the statement, you can write:
“… limited by nitrogen availability (1-3, 5).”
In the reference list
When using the Vancouver style, your reference list should be arranged in the numerical order of which they appeared in the text (remember to include the reference’s number at the beginning of each reference).
The following reference list example is in the style described in “Citing medicine: the NLM style guide for authors, editors, and publishers”. The first reference is a fictive book and the four next references are fictive articles. Note that they include different information. If you want to learn more about how different sources are referenced in the Vancouver style, check out the NLM style guide.
Remember that details such as how to write author names, where to use commas and periods, and when to use italics and bold vary between journals.
Reference list example
- 1. Turner VM, Peterson V. Nutrients and ecosystems. Bergen: Reference List Press. 2001. 502 p.
- 2. Johnson KS. Terrestrial ecosystems – a review. J Hyp Ex. 2019;45(5):34-47.
- 3. Johnson KS, Turner VM, Allen RM. Phosphorus and nitrogen in marine and terrestrial ecosystems. J Ref Ex. 2017;35(1):342-350.
- 4. Allen RM, Peterson V. Phosphorus in freshwater. J Fak Art. 2018;1(3):20–34.
- 5. Johnson KS, Turner VM. Nitrogen availability limits terrestrial ecosystems. Ex Rev. 2018;3(2):345-363.
When you are writing a scientific text, you can quickly end up with a lot of references to keep track of. One way to easily collect, use and navigate through your references is by using a reference management program.
Reference management programs
Here at UiB, you have access to EndNote, which is a reference management program used by many scientists. Other good options are Mendeley and Zotero, both of which are free to use for everyone. These programs allow you to create your own searchable libraries with the references you have read or want to read. They can also help you to cite your sources and create reference lists in different referencing styles.
Help with reference management
The university library at UiB offers courses to those interested in learning how to use EndNote. They also offer advice on Mendeley and Zotero. As a student or staff at UiB you can actually book a librarian for an hour to get help with information searches and reference management! Visit the university library website for more information.