Copying renaming and adjusting exising file how to give credit to original developer

OK so i couldn't think of an appropriate thread title

lets say i am writing a contribution and my contribution is a slight variant on some existing files, for my contribution to work I need to copy, edit the appropriate functions and rename these files, now these files have something like the below at the top of the file

/**
 * @package admin
 * @copyright Copyright 2003-2006 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: new_product_preview.php 3009 2006-02-11 15:41:10Z wilt $
 */

How do i edit it so that it

1. gives appropriate credit to the people who wrote the original file
2. Fits in with zen standard copyright thingie

Obviously I can't copy the above code to the new file as it will be inaccurate in that the file has a different name/ and date/ version ID etc, ironically this is giving me more of a problem than most of the other bits and pieces i have been working on

Cheers

Try something like this

/**
 * @package admin
 * @copyright Copyright 2003-2006 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 *your description
 *your other info 
 *adapted from new_product_preview.php 3009 2006-02-11 15:41:10Z wilt $
 */  

Thanks for that Kobra,

I was intending to do something very similar, i had just thought i better check out if there is a correct way of doing these things