additional_plugins/serendipity_event_markdown/lib/Michelf/MarkdownInterface.inc.php

<?php

// Use this file if you cannot use class autoloading. It will include all the
// files needed for the MarkdownInterface interface.
//
// Take a look at the PSR-0-compatible class autoloading implementation
// in the Readme.php file if you want a simple autoloader setup.

require_once dirname(__FILE__) . '/MarkdownInterface.php';