Anne Frank’s literary legacy continues to live on.

A rare handwritten poem signed by the famed diarist was sold at auction on Wednesday for €140,000 ($148,620). The identity of the online bidder is unknown, according to The Guardian.

The poem Anne Frank wrote is eight lines and was written for her childhood friend, Christiane van Maarsen. It is addressed “Dear Cri-Cri.”

Van Maarsen’s sister, Jacqueline, is the seller of the poem and stated that she had also received a poem addressed to her from Frank, according to USA Today. “I know that my sister was not as attached to this verse from Anne to her as I am to the verse Anne addressed to me, and that is the reason that I am now putting it up for sale,” van Maarsen said in a letter accompanying the poem.

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Netherlands auction house Bubb Kuyper originally valued the handwritten poem between €30,000 and €50,000 ($32,000 and $53,000).

As for those suspicious of the poem’s authenticity, Anne Frank Foundation spokeswoman Maatje Mostart verified the poem’s authenticity and indicated there is no doubt that it’s actually Frank’s handwriting.

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Frank is most well-known for her diaries chronicling her time as a German-born Jewish teenager hiding in occupied Amsterdam during World War II. Frank and her family were captured late in the war. She died at 15 years old in the Bergen-Belsen Nazi concentration camp, just before it was liberated by Allied forces.

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Anne’s father, Otto Frank, survived the war and published her diaries. This poem is one of only a few handwritten items from the teen, outside of the diaries, to have been recovered.