@ARTICLE{AurouxB08,
 author = {Auroux, D. and Bonnabel, S.},
 title = {Symmetry-based observers for some water-tank problems},
 journal = {IEEE Trans. Automat. Contr.},
 year = {2011},
 volume = {56},
 number = {5},
 pages = {1046--1058},
}