title: How to get two \multicolum in a LaTeX table?
body: <p>I'm trying to get something like this:</p>
  
  <pre><code>---------------------------------
  |  Hello world  |     Again     |
  ---------------------------------
  | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
  ---------------------------------
  </code></pre>
  
  <p>So I wrote:</p>
  
  <pre><code>\begin{tabular}{l|l|l}
  \multicolumn{4}{c}{Población total en millones}
  \multicolumn{4}{c}{Porcentaje de población rural}\\
  \hline
  1975 &amp; 2001 &amp; 2003 &amp; 2015 &amp; 1975 &amp; 2001 &amp; 2003 &amp; 2015\\
  \hline
  10,3 &amp; 15,4 &amp; 16 &amp; 17,9 &amp; 21,6 &amp; 14 &amp; 13 &amp; 9,8
  \end{tabular}
  </code></pre>
  
  <p>But it gives me this error:</p>
  
  <blockquote>
    <p>! Misplaced \omit.
    \multispan ->\omit 
                      \@multispan </p>
  </blockquote>
  
  <p>What can I do?</p>
  
  <p><strong>Edit</strong></p>
  
  <p>Also, how can I get a border between the two columns?</p>
  
  <p>Thanks.</p>