anchor.diff:    <h2> Combining More than two terms</h2>
     Any number of single or multiple word search can be combined using " and " and " or ".
     <h3> Survey search </h3>
  -  If both " and " and " or " are used in a single search then the " and " terms take presidence over the " or ".
  +  If both " and " and " or " are used in a single search then the " and " terms take precedence over the " or ".
     For example search "age and when or weight and height", will search for all variables that have both the words age and when.
  -  Then it will search for all variables that have both weight and heigth.
  +  Then it will search for all variables that have both weight and height.
     The result is the combination of the two searches without duplicates.
     <h3> Other searches </h3>
     Using both " and " and "or " in the same search is not supported and can lead to unexpected results.
  
positive.code:         <li>weight when age 5</li>
          <li>weight when born</li>
        </ul>
      <li>Two terms seperated with " and " age and when</li>
        <ul>
          <li>age when had first beer</li>
          <li>age of mother when born</li>
  
negative.code:     <li>age of mother when born</li>
      <li>weight when age 5</li>
      <li>weight when born</li>
      <li>height of first child</li>
    </ul>
    <h2> Example Search results </h2>
    <ul>
  