Gerlach, Friedhelm. "A Critical Evaluation of Sales Forecasting Methods in the Residential Heating Industry, with Particular Emphasis upon the Methods Used by the Surface Combustion Corporation, of Toledo, Ohio." Master's thesis, Bowling Green State University, 1953. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1669905698733756Chicago Manual of Style (17th edition)