@article{01701995, title = {On the closure of the sum of closed subspaces.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {25}, year = {2001}, pages = {257-267}, doi = {10.1155/S0161171201005324}, zbl = {1007.46026}, language = {en}, url = {http://dml.mathdoc.fr/item/01701995} }
Schochetman, Irwin E.; Smith, Robert L.; Tsui, Sze-Kai. On the closure of the sum of closed subspaces.. International Journal of Mathematics and Mathematical Sciences, Tome 25 (2001) pp. 257-267. doi : 10.1155/S0161171201005324. http://gdmltest.u-ga.fr/item/01701995/