@article{AIHPC_2008__25_1_1_0,
     author = {Duyckaerts, Thomas and Zhang, Xu and Zuazua, Enrique},
     title = {On the optimality of the observability inequalities for parabolic and hyperbolic systems with potentials},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {1--41},
     publisher = {Elsevier},
     volume = {25},
     number = {1},
     year = {2008},
     doi = {10.1016/j.anihpc.2006.07.005},
     mrnumber = {2383077},
     zbl = {1248.93031},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.anihpc.2006.07.005/}
}