On fractional powers of differential operators of principal type
1977 ◽
Vol 2
(10)
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pp. 971-1016
2014 ◽
Vol 45
(4)
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pp. 461-467
2016 ◽
Vol 65
(2)
◽
pp. 209-241
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2014 ◽
Vol 5
(3)
◽
pp. 411-454
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1986 ◽
Vol 11
(14)
◽
pp. 1539-1574
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1967 ◽
Vol 43
(2)
◽
pp. 82-86
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