Complex sentence: Intersection numbers had been rigorously defined (by André Weil as part of his foundational programme 1942--6, and again subsequently), but this did not exhaust the proper domain of enumerative questions.
Split into simpler sentences: Intersection numbers had been rigorously defined (by André Weil as part of his foundational programme 1942--6, and again subsequently). This did not exhaust the proper domain of enumerative questions.