@article{articlef99c2b37,
title   = {Differential invariants for symplectic Lie algebras realized by boson operators},
author = {Barbosa, Marconi Soares and Bernardes, Esmerindo de Sousa},
year = {2004},
doi = {10.1088/0305-4470/37/17/010},
journal   = {Journal of Physics A}
}