A Method for Coding Questionnaires in Market Surveys - Greenberg, Allan (Journal of Marketing, 1949)
https://katalog.adlr.link/Record/ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMTE3Ny8wMDIyMjQyOTUwMDE0MDAzMTQ