%0 Journal Article %T Approximate Controllability of Abstract Discrete-Time Systems %A Herná %A n R. Henrí %A quez %A Claudio Cuevas %J Advances in Difference Equations %D 2010 %I Springer %R 10.1155/2010/695290 %U http://dx.doi.org/10.1155/2010/695290