To coincide with what would have been the 90th birthday of World War II teenage diarist Anne Frank, a trove of letters is being released.
As a young man, Ryan Cooper became a pen pal of Anne's father Otto. He's now donating their correspondence to the US Holocaust Memorial Museum in Washington. In their exchanges, Cooper says Otto counselled him on his own personal struggles.
"Well, we met in 1973, after I had written to him a few months before that," Cooper explains. "And we experienced many interesting things, including him letting me see Anne's original diary."
Anne wrote most of her diaries while she and her family were in hiding in Amsterdam.
Hoping to avoid deportation they hid from the Nazis in Otto Frank's office in the city. But they were discovered and sent to concentration camps, where Anne, her sister and mother were killed. Otto was the sole survivor and eventually died in 1980 aged 91. He published Anne's diaries after the war and dedicated his days to speaking about the atrocities of the Holocaust
Cooper says despite everything Otto was an optimist by nature, as Anne's diaries revealed her to be.
"His focus was to teach about the Holocaust - not so much about the Holocaust, but about tolerance and mankind. He based his hope on the young people. And he got inspiration from the letters that he received, mostly from young people."
Otto and Ryan exchange more than 80 letters in their long-distance friendship.