private static function parse_reference_links( $longdesc ) {
		$description = '';
		foreach ( explode( "\n", $longdesc ) as $line ) {
			if ( 0 === strpos( $line, '#' ) ) {
				break;
			}
			$description .= $line . "\n";
		}

		// Fires if it has description text at the head of `$longdesc`.
		if ( $description ) {
			$links   = array(); // An array of URLs from the description.
			$pattern = '/\[.+?\]\((https?:\/\/.+?)\)/';
			$newdesc = preg_replace_callback(
				$pattern,
				function( $matches ) use ( &$links ) {
					static $count = 0;
					$count++;
					$links[] = $matches[1];
					return str_replace( '(' . $matches[1] . ')', '[' . $count . ']', $matches[0] );
				},
				$description
			);

			$footnote   = '';
			$link_count = count( $links );
			for ( $i = 0; $i < $link_count; $i++ ) {
				$n         = $i + 1;
				$footnote .= '[' . $n . '] ' . $links[ $i ] . "\n";
			}

			if ( $footnote ) {
				$newdesc  = trim( $newdesc ) . "\n\n---\n" . $footnote;
				$longdesc = str_replace( trim( $description ), trim( $newdesc ), $longdesc );
			}
		}

		return $longdesc;
	}