The original charts can be found in the book Perfume by William Kaufman. It's out of print but can be found used online at places like amazon. I greatly edited and updated the chart for my online class. I describe 24 aromatic families, all natural aromatics. Then you have to learn - or be taught - how to conduct the comparison and contrast studies. After you know the aromatics by conducting organoleptic studies. Backwards engineering, as it were.