Extension: There are two kinds of signatures: single (long, short, poor) and double (up and down). Long style is written according to time, name, place and creation reason, short style is written according to source, time, name and place, and poor style is written according to author's name. The name, source and recipient of the work shall be stated in the preceding paragraph, and the year, place and author's name of creation shall be recorded in the next paragraph.