Help Refecence supplier on BO

[Krauser]

Hello community, i try to put on my Back Office product list the column with the "Supplier product reference"

(controllers/admin/AdminProductsController.php)

$this->fields_list['product_supplier_reference'] = array(
'title' => $this->l('Suplier Reference'),
'width' => 40,
'filter_key' => 'refer!name',
);

$this->_join .= ' LEFT JOIN `'._DB_PREFIX_.'supplier` AS supp ON (supp.`id_supplier` = a.`id_supplier`) ';

I have tried many codes and forms but i always end up getting errors similar to this one:
Unknown column 'a.id_product_supplier' in 'on clause'

 

Which is the correct form to put that date?

Sorry for the languaje of the image. But can find "supplier" on the product page.

 

My version is: 1.5.4.1

Edited July 10, 2015 by Krauser (see edit history)

[Krauser]

Someone knows?

 

Thanks.

[Krauser]

Any help?

Thanks.