Example
<select class="form-control" data-onload-select2 multiple>
<option selected value="Denver">Denver</option>
<option selected value="Liptákov">Liptákov</option>
<option value="Moscow">Moscow</option>
<option value="Munich">Munich</option>
<option selected value="Prague">Prague</option>
<option value="Viena">Vienna</option>
</select>