In 1943, Clarke wrote an influential textbook in the field of power engineering, "Circuit Analysis of A-C Power Systems", based on her notes for lectures to GE engineers. This two-volume textbook teaches about her adaption of the symmetrical components system, which she became interested in while working for the second time at GE. This system is a mathematical means for engineers to study and solve problems of power system losses and the performance of electrical equipment. Clarke adopted this system to the three-phase components that is the basis of the electrical grid in the United States. This textbook was used as the basis of education for electrical engineers for many years.