The geometry of second order linear partial differential operators
1983 ◽
Vol 8
(6)
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pp. 643-665
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2007 ◽
Vol 1
(2)
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pp. 225-237
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2008 ◽
pp. 199-212
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2017 ◽
Vol 291
(8-9)
◽
pp. 1240-1268
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2009 ◽
Vol 347
(5-6)
◽
pp. 267-270
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