@article{1183530210,
author = {Retherford, J. R. and James, R. C.},
title = {Unconditional bases and best approximation in Banach spaces},
journal = {Bull. Amer. Math. Soc.},
volume = {75},
number = {5},
year = {1969},
pages = { 108-112},
language = {en},
url = {http://dml.mathdoc.fr/item/1183530210}
}
Retherford, J. R.; James, R. C. Unconditional bases and best approximation in Banach spaces. Bull. Amer. Math. Soc., Tome 75 (1969) no. 5, pp. 108-112. http://gdmltest.u-ga.fr/item/1183530210/