@article{articlef5419b6c,
title   = {On the number of invariants in the strain energy density of an anisotropic nonlinear elastic material with two material symmetry directions},
author = {Aguiar, Adair Roberto and Rocha, Gabriel Lopes da},
year = {2018},
doi = {10.1007/s10659-017-9642-5},
journal   = {Journal of Elasticity}
}