@article{krein_2001,  title={The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Proton},  volume={31},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332001000200007},  DOI={10.1590/S0103-97332001000200007},  number={2},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Krein, G.},  year={2001},  month={Jun},  pages={179–182} }