For a simple example, Zhou Shuren (Lu Xun) died in 1936, and his property rights in copyright expired in 1986, so if you want to quote his famous sentence: "In fact, there is no road in the world, and more people will become roads." Write the sentence as "Lu Xun" (don't write "Zhou Shuren").

However, if you want to quote Gu Cheng's short poem: "The night gave me black eyes, but I used them to find light." There is a problem: Gu Cheng committed suicide on 1993, so the copyright of the poem will not expire until 2043, and your behavior must be approved by Gu Cheng's heirs.