Compare the two fictional source extracts below for the question: is the exhibition open on Sunday? Return exact claim/paraphrase with source ID, evidence offered, agreement or difference, dependence between sources, and unresolved checks. Do not treat agreement as proof. Do not infer current opening dates. Do not browse, contact anyone or invent source details.
A1: A fictional organizer notice says the exhibition opens Saturday and Sunday. No publication date or applicable weekend is supplied.
A2: The organizer notice is the stated basis for its own schedule; no separate confirmation is included.
B1: A fictional visitor guide says the exhibition has weekend opening.
B2: The guide explicitly says its opening information comes from the organizer notice A.
Conclude only what the extracts establish. List the next source check needed before relying on Sunday opening.