Complex sentence: One holds that it was invented generally in the 1970's on football ground terraces, while the other holds that it was invented in the 1960's by Oxford United supporting football hooligans to threaten visting fans.
Split into simpler sentences: One holds that it was invented generally in the 1970's on football ground terraces. While the other holds that it was invented in the 1960's by Oxford United supporting football hooligans to threaten visting fans.