@article{pereira_san gil_carvalho_fernandes_azevedo_2011,  title={Solid state 13C NMR analysis of Brazilian cretaceous ambers},  volume={22},  ISSN={0103-5053},  url={https://doi.org/10.1590/S0103-50532011000100012},  DOI={10.1590/S0103-50532011000100012},  number={1},  journal={Journal of the Brazilian Chemical Society},  publisher={Sociedade Brasileira de Química},  author={Pereira, Ricardo and San Gil, Rosane A. S. and Carvalho, Ismar S. and Fernandes, Antonio Carlos S. and Azevedo, Débora A.},  year={2011},  month={Jan},  pages={92–97} }