[Therion] <symbol-set>s missing from in the Therion Book

I have just started learning Therion, and after drawing up my first survey I got some feedback. The main point was to use local symbols. So I set about trying to convert my survey to use the NSS standard. Reading the Therion Book <https://therion.speleo.sk/downloads/thbook.pdf> it seemed like it wasn't supported, as it is not mentioned on page 51 (along with some other standards that are actually supported). Searching some more I found that it was listed in https://therion.speleo.sk/wiki/_media/therion_symbols_20130407_.pdf along with several other <symbol-set>s not mentioned in the Therion Book. I wasn't sure if if these should be added, and thought i'd send this to make ppl aware. Regards, Felix