The dimensions of the Chinese series paper sizes are defined by the GB/T 148-1997 Chinese paper size standard. This standard documents the ISO series, but it does not follow the same principles. Originating from the Republic of China, 1912-1949, the Chinese format is a custom series known as the D series. It is different from the D Series in Sweden. The aspect ratio is approximately √2. The longest side of a Chinese D Series is exactly two times larger than the short side of the next smallest size.