Sort Products in Front Office by reference

[Christos]

Hi Everyone 

 

I need to change the default sort order to reference i am using version 1.5.4.1 

I have managed to add the sort by reference: A to Z  and reference : Z to A  by adding this two lines in 

products_sort.tpl

<option value="reference:asc" {if $orderby eq 'reference' AND $orderway eq 'asc'}selected="selected"{/if}>{l s='Reference: A to Z'}</option>

 <option value="reference:desc" {if $orderby eq 'reference' AND $orderway eq 'desc'}selected="selected"{/if}>{l s='Reference: Z to A'}</option>

 

But i dont know how to change the default sort order to reference

 

Thanks In Advance 

 

Christos