V. Georgiev et Pp. Schirmer, SPACE-TIME ESTIMATES FOR COMPATIBLE FORMS ASSOCIATED WITH 1ST-ORDER HYPERBOLIC SYSTEMS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 318(12), 1994, pp. 1109-1114
We prove here estimates of Klainerman-Machedon type for non-linearitie
s of compatible type associated with linear symmetric hyperbolic syste
ms. This is accomplished by estimating some Fourier integral operators
arising from the parametrix representation of the solutions.