The correct form to cite the RST Spanish Treebank is the following:

da Cunha, Iria; Torres-Moreno, Juan-Manuel; Sierra, Gerardo (2011). «On the Development of the RST Spanish Treebank». In Proceedings of the 5th Linguistic Annotation Workshop. 49th Annual Meeting of the Association for Computational Linguistics (ACL). Portland, Oregon, USA.

da Cunha, Iria; Torres-Moreno, Juan-Manuel; Sierra, Gerardo; Cabrera-Diego, Luis Adrián; Castro Rolón, Brenda Gabriela; Rolland Bartilotti, Juan Miguel (2011). «The RST Spanish Treebank On-line Interface». In Proceedings of Recent Advances in Natural Language Processing (RANLP). Hissar, Bulgaria. 698-703.