∀某 ∩ u : |∅| < |某 ∩ u| < ∞ ⇒ u ∈ {某}

∀某 ∩ u : |∅| < |某 ∩ u| < ∞ ⇒ u ∈ {某}

a brief study of science festivals sci 1384358400007