Source: https://dspace.mit.edu/bitstream/handle/1721.1/34891/15-783JSpring-2002/NR/rdonlyres/Sloan-School-of-Management/15-783JProduct-Design-and-DevelopmentSpring2002/3E3097DE-5952-43F6-878B-A5F2F515D385/0/6congen.pdf