One is 15 cm wide and 20.5 cm high, and the other is 2 1 cm wide and 30 cm high. Just buy it at this size. Can also be purchased with the book; At present, there are hard leather and soft leather, but there are other forms. Layout: whether the layout quality of table indexes, tables and formulas is commensurate with the three-dimensional part, and whether the spacing between words is suitable for the size and style of words (whether the spacing between dot symbols and other special symbols is suitable for the text font, title font and title font); Is kerning evenly distributed? Whether the line break of the title conforms to the meaning of the text.