ハンス・レヴィー
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(1938). “Generalized integrals and differential equations”. Trans. Amer. Math. Soc. 43 (3): 437–464. doi:10.1090/s0002-9947-1938-1501953-8. MR1501953.
(1938). “On differential geometry in the large. I. Minkowski's problem”. Trans. Amer. Math. Soc. 43 (2): 258–270. doi:10.1090/s0002-9947-1938-1501942-3. MR1501942.
Lewy, Hans; Green, John Willie (1939). Aspects of the Calculus of Variations. Berkeley: U. of California Press; notes by J. W.