Name::isFieldRussian

protected function isFieldRussian($field)
{
	if(!is_string($field) || empty($field))
	{
		return false;
	}
	$regex = $this->getRussianLettersRegEx(mb_strlen($field));
	if($regex)
	{
		return (preg_match($regex, $field) === 1);
	}

	return false;
}