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Zbl 0005.20901
[3] GODNER D. B.:
Projections in normed linear spaces. Trans. Amer. Math. Soc. 69 (1950), pp. 89-108.
MR 0037465
[4] KELLEY J. L.:
Banach spaces with the extension property. Trans. Amer. Math. Soc. 72 (1952), pp. 323-326.
MR 0045940
[5] NACHBIN L.:
A theorem of Hahn-Banach type for linear transformations. Trans. Amer. Math. Soc. 68 (1950), pp. 28-46.
MR 0032932