 word characters was really useful for "finding" the keywords. An example:</p>
<ul>
<li>input: "Timing of replacement therapy for acute renal failure after cardiac surgery"</li>
<li>output: [
  "timing",
  "replacement therapy",
  "acute renal failure",
  "cardiac surgery"
]</li>
</ul>
<p>So we basically split the text when we find:</p>
<ul>
<li>a stopword</li>
<li>a non word character(/,!?. etc) (except from - and ')</li>
</ul>
<p>That's it.</p>
<p>But as there were some problem with some keywords that coi