The abstract and keywords are enclosed in brackets, so there is no need to leave two spaces. Key words don't need to be blank, and the first line of each paragraph is indented by 2 characters. There are format requirements for the publication of papers. Written in bold, left-aligned, with two spaces between abstract and importance, the content is Song Dynasty No.4, and three keywords are written in small four-character bold, with 3-5 keywords.