> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://doc.common-services.com/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# Error: Products with a missing reference

When exporting products, you may see:

> Products having empty references, Product ID: \[2/7, 2/8, 2/9, 2/10, …]

*(Export summary may also show* **_Empty reference_***.)*

The list uses product / combination IDs in the form `1/2` whose **Reference** field is empty.

Example:

![PrestaShop CDiscount empty reference example](https://storage.crisp.chat/users/helpdesk/website/-/3/f/a/8/3fa8ee645cd13200/prestashop-cdiscount-exemple-p_1l19ejn.jpg)

Fill in a **unique** reference for every product / combination:

[Validate your catalog structure](https://doc.common-services.com/en/article/validate-your-catalog-structure-cdiscount-1trq16m/)

Find a product by its ID:

![PrestaShop CDiscount search by ID](https://storage.crisp.chat/users/helpdesk/website/-/3/f/a/8/3fa8ee645cd13200/prestashop-cdiscount-recherche_dsjl70.jpg)