M. Collins, и N. Duffy. ACL '02: Proceedings of the 40th Annual Meeting on Association for Computational Linguistics, стр. 263--270. Morristown, NJ, USA, Association for Computational Linguistics, (2001)
S. Herrmann, A. Jensen, M. Joswig, и B. Sturmfels. (2008)cite arxiv:0808.2383
Comment: 21 pages, 10 figures; rewritten proof of Theorem 4.4 (which was
Theorem 4.3 before) for clarification, several other minor corrections.