TU-9 (Engineering) F224.32 (Economy), so your article classification number is China Library classification number: TU-9 F224.32.

"China Library Classification Number" refers to the classification code obtained by analyzing the theme of scientific and technological documents by using "China Library Classification" and organizing the documents in different categories according to the theme attributes and characteristics of the documents. China Library Classification (formerly known as China Library Classification), referred to as Chinese Library Classification, is a representative large-scale comprehensive classification compiled and published after the founding of the People's Republic of China, and it is the most widely used classification system in domestic libraries today. The first edition of China Library Classification was published in 1975, and the fourth edition was published in 1999. The fourth edition of the revised China Library Classification has added the category of classified materials, which is distinguished from the category of classified books by a "+",so it was officially renamed as China Library Classification, with the abbreviation unchanged. The fourth edition of Library Classification of China comprehensively supplements new themes, expands the category system, and makes the classification keep pace with the development of science and technology. At the same time, standardize categories, improve the reference system and annotation system, adjust the category system, and add sub-tables, so as to obviously strengthen the expansion of categories and the accuracy of classification. China Library Classification is divided into 5 basic classifications and 22 categories. Chinese phonetic alphabet and Arabic numerals are mixed, one letter represents a big category, and the alphabetical order reflects the order of big categories, and the number after the letter is used as a mark.