Quick question, from the context and how the wikipedia article was written I assumed TSL was fairly new, however looking at the dates of the published papers it

Quick question, from the context and how the wikipedia article was written I assumed TSL was fairly new, however looking at the dates of the published papers it all seems be late 90's early 2000's. Is this still in use somehow? I've never heard of it before, even though I've dabbled a bit in image processing from time to time in my line of work.