public function getVariableRefs()
	{
		// It is helpful for this function to return references in the 'value' statment and any filter expressions
		// because the check in XBRL-Formulas that detects xbrlve:unresolvedDependency needs them
		$result = array();
		foreach ( $this->variablesByQName as $qname => $variable )
		{
			$result = array_merge( $result, $variable->getVariableRefs() );
		}

		if ( $this->valueXPath2expression instanceof XPath2Expression )
		{
			$result = array_merge( $result, $this->valueXPath2expression->getParameterQNames() );
		}

		$result = array_unique( $result );

		return $result;
	}