@article{COCV_2008__14_3_604_0,
     author = {Mehrenberger, Michel and Loreti, Paola},
     title = {An {Ingham} type proof for a two-grid observability theorem},
     journal = {ESAIM: Control, Optimisation and Calculus of Variations},
     pages = {604--631},
     publisher = {EDP-Sciences},
     volume = {14},
     number = {3},
     year = {2008},
     doi = {10.1051/cocv:2007062},
     mrnumber = {2434069},
     zbl = {1157.35415},
     language = {en},
     url = {http://www.numdam.org/articles/10.1051/cocv:2007062/}
}