BANGOR, Maine – Bangor High School Principal Paul Butler is working damage control after the student yearbook published a quote attributed to Adolph Hitler under a student’s picture.

Bangor senior Pierre-Luc Bouchard submitted the quote, “Anyone who sees and paints a sky green and the fields blue ought to be sterilized,” for use under his photograph in the yearbook, and school officials did not notice the attribution to Hitler until May 26, after many were already handed out to students, the Bangor Daily News reports.

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Butler told the news site he immediately investigated how and why the quote was published, and school staff recalled as many yearbooks as possible to cover the quote with a special sticker provided by the publishing company. Students who did not bring their yearbooks in for the censorship were sent stickers in the mail.

“I have determined that flaws in the submission and review timeline and process, not flaws in judgement regarding the appropriateness of including such a quote, are the cause of its regrettable appearance in the book,” Butler wrote in an email.

“The yearbook is developed as part of an elective course instructed by a teacher advisor,” he wrote. “As part of the digital publishing process, content is entered into software and reviewed in sections, or signatures, with a series of due dates beginning in the fall.

“This is a case where a middle signature nearing deadline was updated but did not then cycle back to review – resulting in a quote that would not have made its way into publication otherwise,” Butler said.

Bouchard did not respond to a request for comment about his quote selection.

The Daily News points out that Hitler was an aspiring artist who was rejected by the Vienna Academy of Art in 1908 as a youth before fighting in the Bavarian Army in World War I, which helped propel him to the leader of the Nazi Party.

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“After Hitler came to power, certain types of artists became one of his party’s many targets. Censorship was rampant. Many artists were interrogated, vilified, imprisoned or closely watched,” according to the news site.

The incident at Bangor High School follows a similar incident involving several quotes by controversial figures published in a Pennsylvania high school yearbook last week, the Associated Press reports.

Officials at Quaker Valley High School apologized to parents and offered refunds last Wednesday when “offensive” quotes by Joseph Stalin, Adolf Hitler, and ISIS leader Abu Bakr al-Baghdadi made their way into the high school yearbook, according to TribLive.com.

School officials told the news site in a prepared statement that the oversight was “a regrettable mistake, as the school district would never knowingly condone this messaging in a school-sponsored publication.”

“We are well aware of the emotions this has conjured in many of our students and their families, and for that we are sorry,” the statement read. “Though the content of the quotes was reviewed thoroughly, the attributions clearly were not.”

The quote from Hitler read: “Words build bridges into unexplored regions.”

The quote attributed to Stalin read: “Ideas are more powerful than guns. We would not let our enemies have guns, so why would we let them have ideas?”

And the quote “Be just: the unjust never prosper. Be valiant. Keep your word, even to your enemies” was attributed to al-Baghdadi.