Paragraph 1 of Article 31 of the Patent Law stipulates: "An application for a patent for an invention or utility model shall be limited to one invention or utility model, and two or more inventions or utility models belonging to the general inventive concept may be filed as one application." That is to say, if an application includes several inventions or utility models, only one general inventive concept among all these inventions or utility models will be allowed. This is a single requirement of patent application.