What does "Yi Gong" mean in ancient Chinese? Please try to explain in detail in terms. Thank you ~ ~

Book is a collating academic language. In the era without printing, books can only be circulated by copying, and there will be mistakes in copying, including multi-word (Yan Wen), few words (off-text) and upside down (upside down). Later generations will have different versions when sorting out these books. Many times, the same paragraph has different expressions in different versions of the same book, but these expressions are all reasonable. When collating ancient books, it is impossible to list all the different expressions, so we can only use one of them as the base copy and then refer to other different versions for collating. In order to explain this difference, it is often expressed as "one for a certain" in comments, which means that the other version is written for a certain.