Citation
A link an answer gives back to a source. The visible half of how these systems work, and the only half you can audit.
Checkable · the test is below
What it means
When an engine shows numbered sources, those are citations. They tell you what it drew on for that answer, in that run. They do not tell you everything it considered, or why one source won over another.
Why it matters for an HVAC company
Citations are where you find out who is speaking for your trade in your town. Usually it is three or four directories and review platforms rather than any contractor's own website, and that finding redirects a lot of budget.
What would settle it
Count them. For a fixed set of questions, record every domain cited across every run. The list is short and it repeats.
A worked example
Ten questions about AC repair in one market produce 63 citations across four engines. Twenty-two go to one review platform, fourteen to a national directory, nine to a local news site, and four to contractor websites. The contractor spending on their blog was aiming at the smallest slice.