An L³ bound for the trilinear Hilbert transform

Proves that the principal-value trilinear Hilbert transform with shifts $x-t$, $x-2t$, $x-3t$ is bounded from $L^3(\mathbb R)^3$ to $L^1(\mathbb R)$. This resolves the L³ exponent case of the standard conjecture for slopes 1, 2, 3.