Physics_and_Astronomy_Classification_Scheme
The Physics and Astronomy Classification Scheme (PACS) is a scheme developed in 1970[1] by the American Institute of Physics (AIP) for classifying scientific literature using a hierarchical set of codes.[2] PACS has been used by over 160 international journals,[1] including the Physical Review series since 1975. Since 2016, American Physical Society introduced the PhySH (Physics Subject Headings) system instead of PACS.