Question about song indexes

[Reissuleipa]

I've been wondering where all the indexes for the songs come from. For example (JS#), (S#), (#) (# = number). And more importantly is there a some kind of database for all of these?

[johanincr]

from this book:

http://www.jimpress.co.uk/bfs.htm

[Reissuleipa]

Thanks for the info. Not having the book these indexes don't mean much...