https://w3id.org/framester/conceptnet5/data/en/quadratic_integer.n <https://w3id.org/framester/conceptnet5/schema/IsA> <https://w3id.org/framester/conceptnet5/data/en/algebraic_number> <https://w3id.org/framester/conceptnet5/data/en/algebraic_integer> risorse dalla linked data cloud