|s1> => find-topic[words] (|thomas>)
|s2> => find-topic[words] (|thomas> + |ronald>)
|s3> => find-topic[words] (|thomas> + |ronald> + |richard>)
|s4> => find-topic[words] (|thomas> + |ronald> + |richard> + |bill>)
|s5> => find-topic[words] (|thomas> + |ronald> + |richard> + |bill> + |barack>)
|s6> => find-topic[words] (|thomas> + |ronald> + |richard> + |bill> + |barack> + |george>)
|s7> => find-topic[words] (|thomas> + |ronald> + |richard> + |bill> + |barack> + |george> + |james>)
|s8> => find-topic[words] (|thomas> + |ronald> + |richard> + |bill> + |barack> + |george> + |james> + |jimmy>)
|list> => |s1> + |s2> + |s3> + |s4> + |s5> + |s6> + |s7> + |s8>