5. The method of claim 1 , wherein the list is a first list and the method further comprises: obtaining a second list of documents containing related phrases of the first phrase but lacking the first phrase; and ranking the second list of documents in descending order of a ratio of the actual co-occurrence rate and the expected co-occurrence rate; and selecting at least one of the highest ranking documents in the second list to include in a result to the query.
5. The method of claim 1 , wherein the list is a first list and the method further comprises: obtaining a second list of documents containing related phrases of the first phrase but lacking the first phrase; and ranking the second list of documents in descending order of a ratio of the actual co-occurrence rate and the expected co-occurrence rate; and selecting at least one of the highest ranking documents in the second list to include in a result to the query. 6. The method of claim 5 , further comprising: removing documents relating to multiple topics from the second list prior to ranking.