How are chemical shifts referenced in ¹⁹F, ³¹P, etc?

If I understand correctly, the instrument uses the deuterium atoms of the solvent to 'tune' itself, so in ¹H and ¹³C, the chemical shifts are usually quite accurate - only off by a few decimals, which we then manually correct with the software.

But how does this work for other nuclei like ¹⁹F or ³¹P?