Anderson, R.; Christensen, C. & Horowitz, S. Analysis of Residential System Strategies Targeting Least-Cost Solutions Leading to Net Zero Energy Homes: Preprint, article, April 1, 2006; (https://digital.library.unt.edu/ark:/67531/metadc891590/m1/1/: accessed January 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .