Complex sentence: He won the AAA Championship race at San Jose in November 1952, but weeks later, on 4 January 1953, was involved in an accident at Carrell Speedway which left him with terrible head injuries.
Split into simpler sentences: He won the AAA Championship race at San Jose in November 1952. Just a few weeks later, on January 4 1953, he was involved in an accident at Carrell Speedway which left him with terrible head injuries.