https://w3id.org/framester/conceptnet5/data/en/gravitational_field <https://w3id.org/framester/conceptnet5/schema/DerivedFrom> <https://w3id.org/framester/conceptnet5/data/en/gravitational.a> <https://w3id.org/framester/conceptnet5/schema/IsA> <https://w3id.org/framester/conceptnet5/data/en/vector_field> risorse dalla linked data cloud