How to show only non referenced products in the "product reference" widget?
When I create(or edit) "Product display" node in "Product reference" field widget I can chose any product entity.
I don't want to display products that are already referenced to other "Product display". I want to hide them in the "Product reference" field widget.
How can I show only non referenced products in the product reference widget?
P.S. Sorry for by bad English.