"Verifiable references" means reliable and trustworthy sources that can confirm or support the information or claims mentioned.
Full definition
We have
verifiable references and an excellent reputation in the Russian dating industry - Testimonials.
Would you employ a consultant who refused to publish accounts, had
no verifiable references, could not name his last successful customer and refused to disclose his methods of working?
Verifiable references and / or significant employment experience are also important as further proof of your abilities and reliability.
If they refuse, better get GOOD and
VERIFIABLE references.