Complex sentence: Landskrona BoIS attendance record is 18,535, and crowds larger than 10,000 once or twice per year, has been common since the 1950s, especially when the club manages to participate in Allsvenskan.
Split into simpler sentences: Landskrona BoIS attendance record is 18.535, and crows larger than 10.000 once or twice per year, has been common since the 1950's. Especially when the club manages to participate in Allsvenskan.