Guidelines for avoiding plagiarism and self-plagiarism in PhD thesis writing
The PhD School at the Faculty of Health Sciences at SDU aims to produce excellent research, and wishes
to ensure that all PhD theses meet high standards for good scientific practice. Furthermore, the PhD School
at the Faculty of Health Sciences at SDU wishes to ensure that all students are well prepared for a scientific
career. It is important that you fully understand the definitions of plagiarism and self-plagiarism and how
they relate to questionable research practice and scientific misconduct.
Important definitions
Plagiarism
Plagiarism is defined as ‘the acquisition of someone else’s ideas, processes, results, text or special
terms without proper acknowledgement’ and constitutes scientific misconduct.
Scientific misconduct
Scientific misconduct is defined as fabrication, falsification or plagiarism, carried out with intent or
resulting from gross negligence in the planning, execution or reporting of research.
Self-plagiarism
Self-plagiarism is the reuse of one’s own text or figures without clear indication of the reuse. Self-
plagiarism is considered questionable research practice.
Questionable Research Practice
Questionable research practice is defined as the breach of recognized standards for responsible
conduct in research, including the standards put forth in the Danish Code of Conduct.
Plagiarism:
Plagiarism is more than simply using text from another source without giving due credit. It is also the use
of someone else’s ideas, results, methods, special terms or processes, without reference to the original
source. Text from other sources must not be used unless it is in the form of quotation along with a reference
to the original source.
Paraphrasing
Paraphrasing is reformulating or summarizing text written by another author. When this is done appropri-
ately, the words and syntax are your own and the text is markedly different from the original, although
communicating a similar content. When paraphrasing, the original author should always be referenced.
Reusing sections of text where only a few words are changed or rearranged is referred to as inappropriate
paraphrasing. Inappropriate paraphrasing constitutes plagiarism, namely when this occurs in a systematic
fashion.
For examples of appropriate and inappropriate paraphrasing, see https://ori.hhs.gov/plagiarism-9
.
Page 2
Self-plagiarism
Self-plagiarism is the use of your own text or figures, which have previously appeared in a different
context, without indication of the reuse. This is often also referred to as text recycling. Self-plagiarism
is considered questionable research practice, and it is therefore important that you always disclose
any reuse of your own text from previous sources, whether this is an article, an assignment or a
conference paper. Self-plagiarism is problematic for several reasons:
• Published papers and copyright: When you publish a paper in a journal, you no longer own the full cop-
yright to that paper. This means that if you take text or figures directly from that paper and include them
in another scientific work without disclosing where they originally appeared, you are potentially infring-
ing copyright.
• Co-author rights: When you share authorship of a scientific article, you and the co-authors have equal
rights to the contents of that paper. This means that if you reuse text or figures from that paper without
disclosing the original source, you are in effect plagiarizing your co-authors. This could lead to a dispute
and should therefore be avoided. It is important to note that such disputes may emerge at a later stage in
your career, and it is therefore important to be in agreement with your co-authors from the start.
• Transparency and originality: When assessing your thesis, it is important that examiners are able to dis-
tinguish clearly between work done during your PhD and any work, which may have been conducted
prior to your PhD studies. Therefore, you should always be transparent about the original source of text
or figures.
Using your own research papers (submitted or published) in your PhD thesis
When you write your PhD thesis, you may already have published one or more articles on the work carried
out during your PhD, and you may want to use this work in your thesis. However, there are several things
you should be aware of in order to avoid unintentional self-plagiarism.
It is of course acceptable to use your published or submitted articles in your thesis, provided that you have
obtained permission from the publisher for this use. Articles may appear in your thesis as chapters or as
appendices.
Important to note
Many journals only allow you to use the post-print version of your article, meaning
the accepted version of the article, without the publisher’s final formatting. In the
event that your article is submitted, but still under review, you should use the latest
submitted version of your article in your thesis. Always remember to check your
publisher’s guidelines on the reuse of published articles. Most journals, unless open
access, have an embargo period on published articles, meaning that within this pe-
riod you cannot freely use the article. Check your publisher’s rules on this issue.
Page 3
In order to avoid unintentionally self-plagiarizing, consider the following scenarios:
You wish to use your whole article as a chapter in your thesis:
• You must clearly indicate at the beginning of the chapter that the chapter is a published/submitted article
and ensure that the article reference is clearly identifiable.
• Remember to consult your publisher’s guidelines on the reuse of articles and if necessary, obtain a per-
mission for reuse.
• When you use your whole article, you should avoid making changes to the text, although reformatting
for the purposes of fitting the article into the thesis format is of course acceptable (heading style etc.).
You wish to use only parts of your article in a chapter of your thesis:
• You must clearly state, at the beginning of the chapter in question, that it is based on one or more sub-
mitted or published articles, and include clear references to those articles.
• If the section you wish to reuse is short, you may wish to quote your article. Such a quote should be
followed by a reference to the article in question.
You wish to use one or more figures from your article in your thesis:
• You may reuse your figures, if you clearly reference the article where the figure originally appeared.
Note that reusing figures as they appear in your paper may require permission from your publisher.
• Alternatively, you can reformat your figure, in which case permission is not needed, but the article in
which the original figure appeared should still be referenced.
• In the event that the figures appear as part of a whole article, it is not necessary to reference the source
of individual figures, as they are clearly imbedded in the article, for which you have already provided a
reference.
Guidelines on the use of text or content from previous assignments in your thesis:
Using content or text from previous assignments such as master’s theses should only take place with
clear reference to the assignment in question. This is because the PhD thesis should only contain
work that you have actually carried out during your PhD, and all work conducted before your PhD,
should be clearly identifiable as such. Any material resulting from work carried out as a part of a
special course during your PhD enrolment, should also be clearly identifiable as such.
Page 4
Tips
Decide on the format of your thesis, well before you start to write. Discuss the dif-
ferent options with your supervisor. This will help you determine which specific
guidelines you should use when you write.
Speak to your supervisor about writing conventions in your field of study. It is the
responsibility of your supervisor to train and inform you on good scientific prac-
tice as this relates to your field of study.
Check copyright rules and permissions with the journal where you intend to pub-
lish, prior to submitting your paper. If necessary, request permission for use of
your accepted article in your thesis at the time of publication, so that you do not
have to obtain this permission retrospectively.
Always ensure that text reuse from your own research papers is clearly indicated at
the beginning of the chapter in which they appear.
Ensure that you obtain consent from your co-authors if you reuse any text from
If you have questions about the interpretation of the guidelines, please contact your principal
supervisor. If you have questions about the Danish law or the guidelines on plagiarism, you
should contact phd
W
e have obtained permission from DTU to reuse and modify a similar guideline developed at their Univer-
sity.
