Iron Storm Answers for Saturn

Unit upgrade tree

I was wondering if anyone knew if there is a chart listing which units get upgrade to which units? there are a lot of units in the game that you can upgrade to that are not listed in your upgrade tree. i've been playing this game now for 15 plus years and i still don't know all of the units. i enjoy playing as america and germany the most and the amount of tanks that you can upgrade is too much for me to keep track of.