Ir I remember correctly, start with research performed by Dr Mary Ann Cooper of the U of Illinois. Of course Dr Uman's old book (All About Lightning) (if I remember the title) is also good reading.
Learn from well understood concepts. For example, lightning must connect a cloud to earthborne charges maybe five miles away. A shortest path is three mile directly down to a tree. Then four miles through earth.
A cow was standing maybe 30 feet from the tree. Therefore killed by a direct...