The short answer is, it depends.
If you need good quality background information on a topic, books may be your best bet. For example, if you are trying to give background information on a theory, books are likely to go into the most detail and give you information on the academic, artist, etc. who came up with the theory.
If you are doing a
academic journals are a good source. You may also be able to use conference proceedings and dissertations/theses for this purpose.
Just remember that you will likely be using a combination of sources for your assignments. You may use books for the general theories, journal articles for the most current research, and you may even be using newspapers and magazines for up-to-date information on industry and trends.
Use books to get a thorough understanding of a topic. Academic books are a useful source for proven theories and detailed explanations of the background knowledge you will need to understand further research in the field. Academic books are a trusted source of information because they are written by experts and usually edited by peers before they can be published. They will also contain a full reference list of sources used and often an index to help you quickly find the information you need.
Image by Nicole Martin/CC license
Academic journals are scholarly publications, usually published on a monthly or yearly basis. They are written by researchers and their primary audience is other experts. They often focus on a single piece of research or case study, but can also be literature reviews or systematic reviews that compare research from several articles. Many of these publications require that articles are "peer reviewed", meaning that they are reviewed by other experts for things like validity and reliability, before they can be published. They will also contain a full reference list or bibliography. Journals are a great source for informing your own research or professional practice.
Probation Journal: SAGE journals/CC license
Trade magazines are non-academic publications written for practitioners in a certain field. They usually cover trends and other current events within an industry or field of practice. They can be a good source of industry information, but be careful to check the publication date as this type of source can quickly become obsolete and only good for historical reference.
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Popular magazine articles are usually written by journalists or freelance writers and are tailored to a general audience. They can be useful for introduction to a topic or for learning current trends. They do not often include references, however, so it can be difficult to discern how reliable the information is.
Ms. Magazine Cover: Winter 2015/Ms. Magazine/CC license
Websites are often the first place people go to learn about a topic. They are highly accessible to anyone with a computer and internet connection and are often a good source of up-to-date information. The free content on the web is usually written for a wide-audience and is therefor free of technical jargon. Of course, anyone can add a webpage to the internet so it is important to evaluate the quality of the information. It can also be frustrating to run into pay-walls where the content is not free.
https and padlock in website address bar/Santeri Viinamäki/CC license
Most newspapers can be accessed online, although not all are free to read. Newspapers and news websites can be a great source for current events. They are not without bias, however. Be aware of the political slant of the newspaper and don't expect the content to be completely objective. It is a good idea to read papers with the opposite bias to get a fuller picture of certain issues.
Social media such as Twitter can be a useful source of current events and even industry information. Be aware, however, that social media is also used by both nefarious and unwitting individuals to share fake news. It is a good idea to check the information for truth before using or sharing with others.
When searching through databases, you may find conference proceedings. This source is usually a compilation of papers and research that has been presented at a conference. It is not unusual to find that the information in these proceedings has also been published in other scholarly publications such as academic journals.
Both theses and dissertations are scholarly works written by students within a graduate program. They have not been published, nor peer-reviewed, but have been written with the guidance of a major professor and academic committee.
The UK government publishes reports of statistics, data, white papers, consumer information, health guidelines, legislation, and more. This is usually considered to be a reliable source of information. When searching for government documents online, make sure that the URL ends in gov.uk.