Gy's sampling theory is a theory about the sampling of materials, developed by Pierre Gy from the 1950s to beginning 2000s in articles and books including: * (1960) Sampling nomogram * (1979) Sampling of particulate materials; theory and practice * (1982) Sampling of particulate materials; theory and practice; 2nd edition * (1992) Sampling of Heterogeneous and Dynamic Material Systems: Theories of Heterogeneity, Sampling and Homogenizing * (1998) Sampling for Analytical Purposes The abbreviation "TOS" is also used to denote Gy's sampling theory.