However, all the notes from his time in prison on display are originals.
The 66 pages of paper were intended to be used by prisoners to write "self-criticism".
In the notes, Mu Xin "converses" with Western masters like William Shakespeare, Leo Tolstoy and Frederic Chopin.
Speaking about the notes, Xu says: "He didn't feel lonely in prison. He felt he was with those masters. The words he wrote were a way for him to express his own emotions."
When the manuscripts were first revealed to the public in the US, Mu Xin told Tong Ming, a professor from California State University, that he could not recognize them.
The writings were on both sides of the paper, and there were more than 10,000 characters on each A4-size paper.
Mu Xin also said that he did not want the notes to be interpreted since it was a way of surviving.
So, Xu says: "We respect the artist's wish not to interpret it or publish it. In history, many intellectuals wrote in prison as a way of 'spiritual salvation'."
Mu Xin moved to the US in 1982. And though he struggled to live by working at antique stores, he never stopped writing and painting, says Chen Danqing, who met Mu Xin in New York.
It was only from 1984 when his articles were published in Taiwan that Mu Xin could make a decent living, and after that he wrote diligently, up to more than 10,000 words per day.
Zhan Hongzhi, an editor in Taiwan who published Mu Xin's articles, recalled that when he first met Mu Xin in New York in the 1980s, he was impressed by the artist's poise and humor, though he was in dire straits.
"I found no trace of suffering on his face," says Zhan, adding that Mu Xin never spoke of the hard times.
Mu Xin kept a very low profile. And according to Chen, he did not show up at the opening ceremony of his solo show in the US.
He told Chen that it's the art that matters, not the artist.
Art, literature and music were Mu Xin's spiritual shelter, says Chen.
