GTIN on packing slip

Need to include gtin on the packing slip.

was including 
and also try with

but no succés, any one that know the answer?

/Nick

Try .  Be aware my mobile keyboard only shows apostrophe for single-quote so I’m not sure how it comes out.

Adjusting your keyboard error  

Thanks for your help.

What file is this statement put in and where is the file found?
Where in the file do you insert the statement??

includes/templates/default.catalog/pages/printable_packing_slip.inc.php

Thanks. Litecart is a great system as it's simple and has a lot of flexibility.