Classification of second-order partial differential equation systems elliptic in the petrovskii sense
2019 ◽
Vol 70
(10)
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pp. 1585-1593
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2003 ◽
Vol 22
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pp. 423-463
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1922 ◽
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pp. 76-81
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Vol 78
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pp. 18095-18112
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2006 ◽
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pp. 223-234
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