Doesn't suit? No problem! You can return within 30 days
You won't go wrong with a gift voucher. The gift recipient can choose anything from our offer.
30-day return policy
In the spring of 1985, A. Casson announced an interesting invariant of homology 3-spheres via constructions on representation spaces. This invariant generalizes the Rohlin invariant and gives surprising corollaries in low-dimensional topology. In the fa