An unbiased Hessian representation for Monte Carlo PDFs Stefano Carrazza, Stefano Forte, Zahari Kassabov, José Ignacio Latorre and Juan Rojo Eur. Phys. J. C, 75 8 (2015) 369 Published online: 12 August 2015 DOI: 10.1140/epjc/s10052-015-3590-7