Complex sentence: Corinthian-Casuals F.C. are a football club currently playing in the Isthmian League First Division, formed in 1939 by a merger of two famous amateur clubs, Corinthians, who formed in 1882, and Casuals, who formed in 1883.
Split into simpler sentences: Corinthian-Casuals F.C. are a football club currently playing in the Isthmian League First Division. They were formed in 1939 by a merger of two famous amateur clubs, Corinthians F.C., who formed in 1882, and Casuals F.C., who formed in 1883.