1, -tp67/J04: tp67 indicates the classification number of books under the category of "industrial technology", and J04 indicates the classification number of books under the category of "computing technology".

2.-G642/ 1K-63: G642 stands for the classification number of the book in the category of "Geography and Tourism", 1K stands for the classification number of the book in this category, and 63 stands for the specific number of the book.

3.-k837/2: k837 indicates the classification number of the book under the category of "Law", and 2 indicates the second specific classification number under this category.