title: How to find duplicates values and keep only those rows?
body: <p>I am checking an huge Open Office Calc list on multiple values in column C.</p>
  
  <p>I have a file like this</p>
  
  <pre>
  A        B      C
  jan 1    Joop   35,90
  jan 1    Kees   80,10
  jan 2    Joep   79,99
  jan 4    Kip    14,88
  jan 4    Roel   15,66
  jan 8    Riep   35,90
  jan 9    Jaap   15,66
  </pre>
  
  <p>I would like tho find all the rows which have a value in column C that is a duplicate of another cell from C (so ignore column A and B). I would like to get output like this:</p>
  
  <pre>
  A        B     C 
  jan 1    Joop  35,90
  jan 4    Roel  15,66
  jan 8    Riep  35,90
  jan 9    Jaap  15,66
  </pre>
  
  <p>Can you guys help me to achieve this?</p>