@article{franco jr._roberts_2004,  title={Surface mechanical analyses by Hertzian indentation},  volume={50},  ISSN={0366-6913},  url={https://doi.org/10.1590/S0366-69132004000200005},  DOI={10.1590/S0366-69132004000200005},  number={314},  journal={Cerâmica},  publisher={Associação Brasileira de Cerâmica},  author={Franco Jr., A. and Roberts, S. G.},  year={2004},  month={Apr},  pages={94–108} }