You won't find such an article that applies to TAX YEAR 2018 and later.
You lost the ability to deduct work expenses like that in exchange for a higher standard deduction and tax cuts for the top 1%.
There wasn't anything specific for firefighters in previous years, just that as with any other trade, you could deduct ordinary and necessary expenses (such as work clothes, and other reimbursed expenses). That's is GONE now.
Sorry.