Unsupervised Topic Identification by Integrating Linguistic and Visual Information Based on Hidden Markov Models Tomohide Shibata author Sadao Kurohashi author 2006-07 text Proceedings of the COLING/ACL 2006 Main Conference Poster Sessions Association for Computational Linguistics Sydney, Australia conference publication shibata-kurohashi-2006-unsupervised https://aclanthology.org/P06-2097/ 2006-07 755 762