@article{EJDE_2007__2007__a22,
     author = {Sharma,  Jaita Pankaj and George,  Raju K.},
     title = {Controllability of matrix second order systems: a trigonometric matrix approach},
     journal = {Electronic journal of differential equations},
     year = {2007},
     volume = {2007},
     zbl = {1136.93311},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2007__2007__a22/}
}