Linked from
The 59 pages that link to Hydrogen, each with the reason it gives.
DeuteriumNarrower topic: Deuterium belongs to hydrogen because its nucleus contains one proton.
Power-to-XNarrower topic: Many Power-to-X pathways use hydrogen as an intermediate molecule.
Hydrazoic acidNarrower topic: Its single hydrogen atom is the proton-bearing part of the acid.
HydronNarrower topic: Hydrons are positively charged forms of hydrogen atoms or nuclei.
Semiheavy waterNarrower topic: Its isotope variety makes distinct water isotopologues possible.