Complex sentence: It stood as the record for a long time, until the first computer analysis, which was done at Bell Labs, in 1990, by David Applegate, Guy Jacobson, and Daniel Sleator.
Split into simpler sentences: It stood as the record for a long time, until the first computer analysis. It was done at Bell Labs, in 1990, by David Applegate, Guy Jacobson, and Daniel Sleator.