To Study is to Learn... To Learn is to Understand... To Understand is to Appreciate... To Appreciate is to Value... To Value is to Save
This link is to a site that may be quite useful to us in our study...than again, maybe it's biased... Who created it? What is their purpose? Are they reliable? At a glance it seems okay. I leave you to investigate further. It may help answer some of your questions.
Enjoy the rainy day off. I'm enjoying making feeding stations for waxeyes and some kind of finch that has appeared in my garden lately.