@article{ludwig_1997,  title={Theoretical Methods in the Design of the Poloidal Field Coils for the ETE Spherical Tokamak},  volume={27},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97331997000300009},  DOI={10.1590/S0103-97331997000300009},  number={3},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Ludwig, Gerson Otto},  year={1997},  month={Sep},  pages={392–397} }