@article{sandoval junior_2002,  title={Sewing string tree vertices with ghosts},  volume={32},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332002000100035},  DOI={10.1590/S0103-97332002000100035},  number={1},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Sandoval Junior, Leonidas},  year={2002},  month={Mar},  pages={232–254} }