@article{rocha_costa_2006,  title={Fracture toughness of Si3N4 processed by gas pressure sintering and hot pressing},  volume={9},  ISSN={1516-1439},  url={https://doi.org/10.1590/S1516-14392006000200006},  DOI={10.1590/S1516-14392006000200006},  number={2},  journal={Materials Research},  publisher={ABM, ABC, ABPol},  author={Rocha, Cláudio V. and Costa, Célio A.},  year={2006},  month={Apr},  pages={143–146} }