Controversial Milwaukee County Sheriff David Clarke, who this week announced he will be joining Donald Trump’s administration as assistant secretary in the Department of Homeland Security, plagiarized sections of his 2013 master’s thesis on US security, a CNN KFile review has found.

Clarke, a visible surrogate for Trump during the campaign known for his incendiary rhetoric, earned a master’s degree in security studies at the Naval Postgraduate School in Monterey, California. In his thesis, “Making U.S. security and privacy rights compatible,” Clarke failed to properly attribute his sources at least 47 times.

In all instances reviewed by CNN’s KFile, Clarke lifts language from sources and credits them with a footnote, but does not indicate with quotation marks that he is taking the words verbatim.

According to guidelines on plagiarism posted on the Naval Postgraduate School’s website, “If a passage is quoted verbatim, it must be set off with quotation marks (or, if it is a longer passage, presented as indented text), and followed by a properly formulated citation. The length of the phrase does not matter. If someone else’s words are sufficiently significant to be worth quoting, then accurate quotation followed by a correct citation is essential, even if only a few words are involved.”