@article{1183491960, author = {Langer, R. E.}, title = {Three theorems on closure of biorthogonal systems of functions}, journal = {Bull. Amer. Math. Soc.}, volume = {33}, number = {6}, year = {1927}, pages = { 97-105}, language = {en}, url = {http://dml.mathdoc.fr/item/1183491960} }
Langer, R. E. Three theorems on closure of biorthogonal systems of functions. Bull. Amer. Math. Soc., Tome 33 (1927) no. 6, pp. 97-105. http://gdmltest.u-ga.fr/item/1183491960/