Now that dissertations and theses are available online, they are "virtual publications" and often viewed and/or downloaded by interested parties worldwide. For example, SHU School of Health & Medical Sciences dissertations have been downloaded over 20,000 (yes, that's twenty THOUSAND) times since we began placing then online in 2011.
The wide availability and interest in dissertations and theses means that we must be vigilant in observing copyright restrictions. Most published content (including material found on the internet) is subject to copyright unless it was created prior to 1923, is a US government publication, or is explicitly published as "open access".
We all know that we must cite all the sources that we use when writing a dissertation or theses (just as we would in a journal article or book) but did you know that images such as figures and tables must also be cited? Not only must they be cited, but some publishers require that you obtain their permission to use images that appear in journals or books that they publish.
Publisher that require permission to use images include Elsevier, Wiley, Springer, Taylor & Francis, and Sage.
If you are not sure whether you need to obtain permission to re-use an image or a substantial portion of text, check the publisher's website or the Copyright Clearnce Center's Obtaining Permission page.