Chemical building blocks in quantum chemical calculations. Perspective on "The density matrix in many-electron quantum mechanics I. Generalized product functions. Factorization and physical interpretation of the density matrices" - McWeeny R (1959) Proc R Soc Lond Ser A 253 : 242-259

The group function theory described in the title paper of McWeeny is overvi ewed by pointing out its influence on different fields of theoretical chemi stry, in particular its serving as a general framework for various forms of building blocks and local treatments of extended systems.