public function setAreaMapEntries(AreaMapEntryCollection $areaMapEntries)
    {
        if (count($areaMapEntries) >= 1) {
            $this->areaMapEntries = $areaMapEntries;
        } else {
            $msg = "An AreaMapping object must contain at least one AreaMapEntry object. none given.";
            throw new InvalidArgumentException($msg);
        }
    }