Georgi, Pati and Quinn were honoured for their "pioneering contributions to the quest for a unified theory of quarks and leptons and the strong, weak and electromagnetic interactions." Working with Salam, Pati developed the first gauge theory version of the standard model. Working with Sheldon Glashow - who shared the 1979 Nobel Prize for Physics with Salam and Steven Weinberg - Georgi discovered many of the most significant models for the grand unification of the strong and electroweak forces. Quinn is best known for her work on charge-parity symmetry. Georgi, Quinn and Weinberg also did important work together on unification.