Complex sentence: Hill and his collaborator John Ernest were two constructionist artists fascinated by mathematics, who not only formulated this problem but also originated a conjectural formula for this crossing number, which Richard K. Guy published in 1960.
Split into simpler sentences: Hill and his collaborator John Ernest were two constructionist artists fascinated by mathematics. They not only formulated this problem but also originated a conjectural formula for this crossing number, which Richard K. Guy published in 1960.