1. L. Hörmander, The Analysis of Linear Partial Differential Operators (Springer-Verlag, Berlin, 1983).
2. H. G. Ghazaryan, V.N. Margaryan. “On solutions of Cauchy problem of h hyperbolic equations”, J.ContemporaryMathematical Analysis (Armenian Academy of Sciences), (in print).
3. L. Hörmander, “On Interior Regularity of Solutions of Partial Differential Equations”, Comm. Pure. Appl. Math., 11, 197–218, 1956.
4. V. N. Margaryan, G. H. Hakobyan, “On Gevrey Type Solutions of Hypoelliptic Equations”, J. Contemporary Mathematical Analysis (Armenian Academy of Sciences), 31 (2), 33–47, 2002.
5. H. G. Ghazaryan, V.N. Margaryan, “On weighted hyperbolic polynomials”, J. Contemporary Mathematical Analysis (Armenian Academy of Sciences), 49 (5), 212–223, 2014.