no. 3
Holomorphic perturbation of a system of micro-differential equations
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 5 (1978) no. 3, pp. 581-586. 
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Kawai, Takahiro. Holomorphic perturbation of a system of micro-differential equations. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 5 (1978) no. 3, pp. 581-586. http://archive.numdam.org/item/ASNSP_1978_4_5_3_581_0/

[1] T. Kawai, Invariance of cohomology groups under a deformation of an elliptic system of linear differential equations, Proc. Japan Acad., 53 (1977) pp. 144-145. | MR | Zbl

[2] H. Lewy, On analyticity in homogeneous first order partial differential equations, Ann. Scuola Norm. Sup. Pisa, serie IV, 3 (1976), pp. 719-723. | Numdam | MR | Zbl

[3] M. Sato - T. Kawai - M. Kashiwara (referred to as S-K-K [3]), Microfunctions and pseudo-differential equations, in Lecture Notes in Math., no. 287, pp. 265-529, Berlin - Heidelberg - New York: Springer (1973). | MR | Zbl

[4] M. Zerner, Sur les perturbations analytiques, Astérisque, 2 et 3 (1973), pp. 363-370. | Numdam | MR | Zbl