You should see these three words on an inscription or inscription, and there should be a name in front of it.
This means that this passage was written by someone, not Dan. "Text" refers to the content of the text, that is, who is the author of this text; "Book" refers to calligraphy, and "harmony" refers to writing, which refers to the person who wrote this passage down.
Usually, "writing" and "book" can be written by one person or two people, such as Zhang San and Li Si (because Li Si's calligraphy is better than Zhang San's, or is famous), that is, a sentence is attached to this passage: "Zhang San wrote Li Si's Book of a Month in Qing Dynasty". If the same person writes, it will be written as "Zhang San wrote a book about a month in the Qing Dynasty"