PACS - Physics and Astronomy Classification Scheme (AIP)
Physics and Astronomy Classification Scheme® (PACS®) is an internationally adopted, hierarchical subject classification scheme, designed by the American Institute of Physics (AIP) to classify and categorize the literature of physics and astronomy. The Physics and Astronomy Classification Scheme® (PACS) was developed by the American Institute of Physics (AIP) and has been used in Physical Review since 1975 to identify fields and sub-fields of physics. PACS is a hierarchical partitioning of the whole spectrum of subject matter in physics, astronomy, and related sciences.