public function addAnd($p1, $p2 = null, $p3 = null)
 {
     if (is_null($p3)) {
         return parent::addAnd($p1, $p2, $p3);
     }
     // addAnd(column, value, comparison)
     $nc = new SphinxCriterion('SphinxEntryDistributionCriteria', $this, $p1, $p2, $p3);
     $oc = $this->getCriterion($p1);
     if (!is_null($oc)) {
         // no need to add again
         if ($oc->getValue() != $p2 || $oc->getComparison() != $p3) {
             $oc->addAnd($nc);
         }
         return $this;
     }
     return $this->add($nc);
 }