<p>XTRACT was a tool for lexical collocation developed in the 1980s and early 1990s. More information on its development and functionality may be found in the following:</p> <p>Smadja, Frank. \"Retrieving Collocations from Text: XTRACT.\" <em>Computational Linguistics</em> 19.1 (1993): 143-177. <a href=\"http://acl.ldc.upenn.edu/J/J93/J93-1007.pdf\" target=\"_blank\">Web</a>.</p> <p>Smadja, Frank. \"XTRACT: An Overview.\" <em>Computers and the Humanities</em> 26.5-6 (1992): 399-413. <a href=\"http://www.jstor.org/stable/30204633\" target=\"_blank\">Web</a>.</p>