tion
         <ul>
             <li><a href="http://lucene.apache.org/core/5_1_0/core/org/apache/lucene/search/similarities/LambdaDF.html?is-external=true" title="class or interface in org.apache.lucene.search.similarities"><code>DF</code></a>: <code>N<sub>w</sub>/N</code> or average
                 number of documents where w occurs</li>
             <li><a href="http://lucene.apache.org/core/5_1_0/core/org/apache/lucene/search/similarities/LambdaTTF.html?is-external=true" title="class or interface in org