Complex sentence: In 1973, Stebbins gave his last lectures at UC Davis, he was made emeritus professor, and following his retirement travelled widely, taught and visited colleagues for another for the next 20 years.
Split into simpler sentences: In 1973, Stebbins gave his last lectures at UC Davis and was made professor emeritus. Following his retirement, he travelled widely, taught, and visited colleagues for the next 20 years.