Li-Zingers hyperplane theorem states that the genus one GW-invariants of the quintic threefold is the sum of its reduced genus one GW-invariants and 1/12 multiplies of its genus zero GW-invariants. We apply the Guffin-Sharpe-Wittens theory (GSW theor
y) to give an algebro-geometric proof of the hyperplane theorem, including separation of contributions and computation of 1/12.
