Spring, H. M. 1., & Kohan, A. L. (1981). Boiler operator's guide: Boiler construction, operation, inspection, maintenance and repair, with typical boiler questions and answer for plant operating, and maintenance engineers (2. edition --.). New York, New York: McGraw-Hill.

Spring, Harry Mortimer 1908-, and Anthony Lawrence Kohan. Boiler Operator's Guide: Boiler Construction, Operation, Inspection, Maintenance and Repair, With Typical Boiler Questions and Answer for Plant Operating, and Maintenance Engineers. 2. edition --. New York, New York: McGraw-Hill, 1981.

Spring, Harry Mortimer 1908-, and Anthony Lawrence Kohan. Boiler Operator's Guide: Boiler Construction, Operation, Inspection, Maintenance and Repair, With Typical Boiler Questions and Answer for Plant Operating, and Maintenance Engineers. 2. edition --. New York, New York: McGraw-Hill, 1981.