@Misc{ ferfraver10, author = { Ferrari, Fausto and Franchi, Bruno and Verbitsky, Igor }, title = { Hessian inequalities and the fractional Laplacian }, journal = { J. Reine Angew. Math. }, year = { 2010 }, pages = { }, URL = { http://cvgmt.sns.it/paper/564/ }, note = { cvgmt preprint} }