What do these symbols and alpha numeric coding mean

Has anyone a reference source for the explanation of these,please refer to attachments, small pix taken from the larger.


2010-01-27_115937.jpg

-CG = Negative Cloud to Ground Strike
+CG = Positive Cloud to Ground
-IC and +IC = Cloud to Cloud

+CG’s are the big ones.

Thanks Niko, that is a great help.
Rob.