As huge amounts of knowledge are created rapidly, effective information access becomes an important issue. Especially for critical domains, such as medical and financial areas, efficient retrieval of concise and relevant information is highly desired. In this paper we propose two new multi-document summarization techniques that make use of WordNet, a general knowledge source from Princeton University. We participated in the Text Analysis Conference 2008 update summarization task and ranked in the middle tier of about 70 systems.